diff --git a/.eslintignore b/.eslintignore
index a843dc4..1c1d90d 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -1 +1,2 @@
 test/fixtures
+test/macroFixtures
diff --git a/.prettierignore b/.prettierignore
index 0a59b7e..bc0e285 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -1 +1,2 @@
 test/fixtures/**/output.js
+test/macroFixtures/**/output.js
diff --git a/lib/evaluateExpression.js b/lib/evaluateExpression.js
index 9de71fd..0512a52 100644
--- a/lib/evaluateExpression.js
+++ b/lib/evaluateExpression.js
@@ -1,8 +1,11 @@
+/* eslint-disable no-console */
 const { types: t, transformFileSync } = require('@babel/core');
 const nodePath = require('path');
 
 function evaluateExpression(path, expression, env) {
   const evaluateFns = [
+    [t.isTaggedTemplateExpression, evaluateTaggedTemplateExpression],
+    [t.isTemplateLiteral, evaluateTemplateLiteralExpression],
     [t.isLiteral, evaluateLiteral],
     [t.isIdentifier, evaluateIdentifier],
     [t.isMemberExpression, evaluateMemberExpression],
@@ -24,10 +27,10 @@ function evaluateExpression(path, expression, env) {
 }
 
 function evaluateLiteral(path, expression, env) {
-  if (expression.type !== 'TemplateLiteral') {
-    return expression.value;
-  }
+  return expression.value;
+}
 
+function evaluateTemplateLiteralExpression(path, expression, env) {
   const quasis = expression.quasis;
   const literals = [quasis[0].value.cooked];
   const expressions = [];
@@ -68,15 +71,14 @@ function evaluateIdentifier(path, expression, env) {
 
     const initPath = binding.path.get('init');
     if (initPath.node) {
-      return evaluateExpression(initPath, initPath.node, env);
+      return evaluateExpression(path, initPath.node, env);
     }
   } else if (expression.name === 'undefined') {
     return undefined;
   }
 
   throw new Error(
-    `babel-plugin-glsl: cannot resolve glslify() call, unknown or non-initialized identifier "${
-      expression.name
+    `babel-plugin-glsl: cannot resolve glslify() call, unknown or non-initialized identifier "${expression.name
     }"`
   );
 }
@@ -109,8 +111,7 @@ function evaluateImport(importPath, env) {
               exit(path) {
                 if (!exprToevaluate) {
                   throw new Error(
-                    `babel-plugin-glsl: cannot resolve glslify() call, import "${
-                      importPath.node.local.name
+                    `babel-plugin-glsl: cannot resolve glslify() call, import "${importPath.node.local.name
                     }" not exported by "${src}"`
                   );
                 }
@@ -129,6 +130,7 @@ function evaluateMemberExpression(path, expression, env) {
   const { property, object, computed } = expression;
 
   if (['window', 'self', 'global', 'globalThis'].includes(object.name)) return expression;
+
   const objectValue =
     object.name === 'Math' ? Math : evaluateExpression(path, object, env);
 
@@ -166,13 +168,13 @@ function evaluateUnaryExpression(path, expression, env) {
 
   // prettier-ignore
   switch (expression.operator) {
-      case '+': return +value
-      case '-': return -value
-      case '!': return !value
-      case '~': return ~value
-      case 'typeof': return typeof value
-      case 'void': return void value
-    }
+    case '+': return +value
+    case '-': return -value
+    case '!': return !value
+    case '~': return ~value
+    case 'typeof': return typeof value
+    case 'void': return void value
+  }
   throw new Error(
     `babel-plugin-glsl: unsupported unary operator "${expression.operator}"`
   );
@@ -186,26 +188,26 @@ function evaluateBinaryExpression(path, expression, env) {
 
   // prettier-ignore
   switch (expression.operator) {
-          case '+': return left + right
-          case '-': return left - right
-          case '*': return left * right
-          case '&': return left & right
-          case '/': return left / right
-          case '%': return left % right
-          case '|': return left | right
-          case '^': return left ^ right
-          case '||': return left || right
-          case '&&': return left && right
-          case '<<': return left << right
-          case '>>': return left >> right
-          case '>>>': return left >>> right
-          case '===': return left === right
-          case '!==': return left !== right
-          case '<': return left < right
-          case '>': return right < left
-          case '<=': return left <= right
-          case '>=': return left >= right
-        }
+    case '+': return left + right
+    case '-': return left - right
+    case '*': return left * right
+    case '&': return left & right
+    case '/': return left / right
+    case '%': return left % right
+    case '|': return left | right
+    case '^': return left ^ right
+    case '||': return left || right
+    case '&&': return left && right
+    case '<<': return left << right
+    case '>>': return left >> right
+    case '>>>': return left >>> right
+    case '===': return left === right
+    case '!==': return left !== right
+    case '<': return left < right
+    case '>': return right < left
+    case '<=': return left <= right
+    case '>=': return left >= right
+  }
   throw new Error('babel-plugin-glsl: unsupported binary expression');
 }
 
@@ -213,13 +215,13 @@ function evaluateArrayExpression(path, expression, env) {
   return expression.elements.map(prop => evaluateExpression(path, prop, env));
 }
 
-function evaluateObjectExpression(path, expression, babel) {
+function evaluateObjectExpression(path, expression, env) {
   return expression.properties.reduce((result, property) => {
     if (property.type !== 'ObjectProperty') {
       throw new Error('babel-plugin-glsl: expected object property');
     }
 
-    const value = evaluateExpression(path, property.value, babel);
+    const value = evaluateExpression(path, property.value, env);
     const key = property.key;
     if (key.type === 'Identifier') {
       result[key.name] = value;
@@ -232,6 +234,10 @@ function evaluateObjectExpression(path, expression, babel) {
   }, {});
 }
 
+function evaluateTaggedTemplateExpression(path, expression, env) {
+  return evaluateExpression(path, expression.node.quasi, env);
+}
+
 function isPrimitive(val) {
   return val == null || /^[sbn]/.test(typeof val);
 }
diff --git a/lib/processGlslTag.js b/lib/processGlslTag.js
index 0b7c406..ec0f0ca 100644
--- a/lib/processGlslTag.js
+++ b/lib/processGlslTag.js
@@ -1,30 +1,44 @@
-const { dirname } = require('path');
+const { readFileSync } = require('fs');
+const { dirname, resolve } = require('path');
 const { types: t } = require('@babel/core');
 const evaluateExpression = require('./evaluateExpression');
 const compile = require('./compile');
 
 function processGlslTag(path, state) {
   const cwd = dirname(state.filename);
-  const env = {
-    cwd,
-  };
-  const literal = evaluateExpression(path, path.node.quasi, env);
+  const env = { cwd };
 
-  if (t.isTemplateLiteral(literal)) {
-    literal.quasis = literal.quasis.map(quasi => {
-      quasi.value.raw = `\n${compile(quasi.value.raw, { basedir: cwd })}`;
-      return quasi;
-    });
-    path.replaceWith(literal);
-    return;
-  } else if (typeof literal === 'string') {
-    const result = compile(literal, { basedir: cwd });
+  if (
+    t.isCallExpression(path.node) &&
+    t.isStringLiteral(path.node.arguments[0])
+  ) {
+    const filename = resolve(
+      dirname(state.filename),
+      path.node.arguments[0].value
+    );
+    const contents = readFileSync(filename, "utf8");
+    const result = compile(contents, { basedir: dirname(filename) });
     path.replaceWith(t.stringLiteral(result));
+    return;
   } else {
-    throw new Error(
-      'babel-plugin-glsl: string template could not be evaluated'
-    );
+    const literal = evaluateExpression(path, path, env);
+    if (t.isTemplateLiteral(literal)) {
+      literal.quasis = literal.quasis.map(quasi => {
+        quasi.value.raw = `\n${compile(quasi.value.raw, { basedir: cwd })}`;
+        return quasi;
+      });
+      path.replaceWith(literal);
+      return;
+    } else if (typeof literal === 'string') {
+      const result = compile(literal, { basedir: cwd });
+      path.replaceWith(t.stringLiteral(result));
+      return;
+    }
   }
+
+  throw new Error(
+    'babel-plugin-glsl: string template could not be evaluated'
+  );
 }
 
 module.exports = processGlslTag;
diff --git a/macro.js b/macro.js
index c512ce6..5308fc1 100644
--- a/macro.js
+++ b/macro.js
@@ -1,12 +1,16 @@
 const { createMacro, MacroError } = require('babel-plugin-macros');
 const processGlslTag = require('./lib/processGlslTag');
 
-function glslifyMacro({ references, state }) {
+function glslifyMacro({ references, state, babel }) {
+  const t = babel.types;
   const { default: defaultImport = [] } = references;
 
   defaultImport.forEach(referencePath => {
     const path = referencePath.parentPath;
-    if (path.type === 'TaggedTemplateExpression') {
+    if (
+      (t.isCallExpression(path.node) &&
+        t.isStringLiteral(path.node.arguments[0])) ||
+      t.isTaggedTemplateExpression(path.node)) {
       try {
         processGlslTag(path, state);
       } catch (e) {
diff --git a/test/macro.test.js b/test/macro.test.js
index 12fefcf..7799f8b 100644
--- a/test/macro.test.js
+++ b/test/macro.test.js
@@ -16,5 +16,13 @@ pluginTester({
       `,
       output: '"\\nvoid main () {\\n  gl_FragColor = vec4(1, 0, 0, 1);\\n}";',
     },
+    {
+      code: `
+        import glsl from '../macro';
+
+        glsl("./macroFixtures/externalFile/myshader.frag");
+      `,
+      output: '"#define E 2.718281828459045\\n#define PI 3.141592653589793\\n\\nvoid main () {\\n  gl_FragColor = vec4(vec3(1.,0.,0.), 1);\\n}\\n";',
+    },
   ],
 });
diff --git a/test/macroFixtures/externalFile/code.js b/test/macroFixtures/externalFile/code.js
new file mode 100644
index 0000000..1f773b7
--- /dev/null
+++ b/test/macroFixtures/externalFile/code.js
@@ -0,0 +1,3 @@
+import glsl from 'glslify';
+
+glsl("./myshader.frag");
diff --git a/test/macroFixtures/externalFile/defines.glsl b/test/macroFixtures/externalFile/defines.glsl
new file mode 100644
index 0000000..1d438ca
--- /dev/null
+++ b/test/macroFixtures/externalFile/defines.glsl
@@ -0,0 +1,2 @@
+#define E 2.718281828459045
+#define PI 3.141592653589793
diff --git a/test/macroFixtures/externalFile/myshader.frag b/test/macroFixtures/externalFile/myshader.frag
new file mode 100644
index 0000000..0d39691
--- /dev/null
+++ b/test/macroFixtures/externalFile/myshader.frag
@@ -0,0 +1,4 @@
+#pragma glslify: import(./defines)
+void main () {
+  gl_FragColor = vec4(#ff0000, 1);
+}
diff --git a/test/macroFixtures/externalFile/output.js b/test/macroFixtures/externalFile/output.js
new file mode 100644
index 0000000..61623c8
--- /dev/null
+++ b/test/macroFixtures/externalFile/output.js
@@ -0,0 +1 @@
+"\n  #define E 2.718281828459045\n#define PI 3.141592653589793\n\n  void main () {\n    gl_FragColor = vec4(vec3(1.,0.,0.), 1);\n  }\n";
\ No newline at end of file
diff --git a/test/macroFixtures/externalFile/package.json b/test/macroFixtures/externalFile/package.json
new file mode 100644
index 0000000..26c04bd
--- /dev/null
+++ b/test/macroFixtures/externalFile/package.json
@@ -0,0 +1,8 @@
+{
+  "glslify": {
+    "transform": [
+      "glslify-hex",
+      "glslify-import"
+    ]
+  }
+}