diff --git a/package.json b/package.json
index 7ae266e..5a00c10 100644
--- a/package.json
+++ b/package.json
@@ -50,7 +50,7 @@
   "size-limit": [
     {
       "path": "dist/index.js",
-      "limit": "2 kB"
+      "limit": "2.1 kB"
     }
   ],
   "ts-scripts": {
diff --git a/src/cases.spec.ts b/src/cases.spec.ts
index 21e38f0..af8be4e 100644
--- a/src/cases.spec.ts
+++ b/src/cases.spec.ts
@@ -146,6 +146,26 @@ export const PARSER_TESTS: ParserTestSet[] = [
       "\\\\:test",
     ),
   },
+  {
+    path: "/:username([a-zA-Z]+)",
+    expected: new TokenData(
+      [
+        { type: "text", value: "/" },
+        { type: "param", name: "username", pattern: "[a-zA-Z]+" },
+      ],
+      "/:username([a-zA-Z]+)",
+    ),
+  },
+  {
+    path: "/:id(\\.(json|xml))",
+    expected: new TokenData(
+      [
+        { type: "text", value: "/" },
+        { type: "param", name: "id", pattern: "\\.(json|xml)" },
+      ],
+      "/:id(\\.(json|xml))",
+    ),
+  },
 ];
 
 export const STRINGIFY_TESTS: StringifyTestSet[] = [
@@ -231,6 +251,15 @@ export const STRINGIFY_TESTS: StringifyTestSet[] = [
     },
     expected: "/:test",
   },
+  {
+    data: {
+      tokens: [
+        { type: "text", value: "/" },
+        { type: "param", name: "username", pattern: "[a-zA-Z]+" },
+      ],
+    },
+    expected: "/:username([a-zA-Z]+)",
+  },
 ];
 
 export const COMPILE_TESTS: CompileTestSet[] = [
@@ -1741,4 +1770,25 @@ export const MATCH_TESTS: MatchTestSet[] = [
       { input: "/123", expected: { path: "/123", params: { test: "123" } } },
     ],
   },
+
+  /**
+   * Pattern.
+   */
+  {
+    path: "/:test(abc|123)",
+    tests: [
+      {
+        input: "/abc",
+        expected: { path: "/abc", params: { test: "abc" } },
+      },
+      {
+        input: "/123",
+        expected: { path: "/123", params: { test: "123" } },
+      },
+      {
+        input: "/xyz",
+        expected: false,
+      },
+    ],
+  },
 ];
diff --git a/src/index.spec.ts b/src/index.spec.ts
index a8e2a0f..7d78ca4 100644
--- a/src/index.spec.ts
+++ b/src/index.spec.ts
@@ -77,6 +77,18 @@ describe("path-to-regexp", () => {
         new PathError("Unterminated quote at index 2", '/:"foo'),
       );
     });
+
+    it("should throw on incomplete pattern", () => {
+      expect(() => parse("/(")).toThrow(
+        new PathError("Unbalanced pattern at index 2", "/("),
+      );
+    });
+
+    it("should throw on missing opening pattern", () => {
+      expect(() => parse("/)")).toThrow(
+        new PathError("Unexpected ) at index 1, expected end", "/)"),
+      );
+    });
   });
 
   describe("compile errors", () => {
@@ -166,6 +178,23 @@ describe("path-to-regexp", () => {
         expect(stack).toContain("index.spec.ts");
       }
     });
+
+    describe("patterns", () => {
+      it("should throw on unsupported pattern", () => {
+        expect(() => pathToRegexp("/:foo(??)")).toThrow(
+          new PathError(
+            'Unsupported pattern "??" for "foo" param',
+            "/:foo(??)",
+          ),
+        );
+      });
+
+      it("should throw on empty pattern", () => {
+        expect(() => pathToRegexp("/:foo()")).toThrow(
+          new PathError('Unsupported pattern "" for "foo" param', "/:foo()"),
+        );
+      });
+    });
   });
 
   describe("stringify errors", () => {
diff --git a/src/index.ts b/src/index.ts
index 052cfb5..32ba30e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -62,6 +62,7 @@ type TokenType =
   | "}"
   | "wildcard"
   | "param"
+  | "pattern"
   | "char"
   | "escape"
   | "end"
@@ -88,7 +89,6 @@ const SIMPLE_TOKENS: Record<string, TokenType> = {
   "{": "{",
   "}": "}",
   // Reserved.
-  "(": "(",
   ")": ")",
   "[": "[",
   "]": "]",
@@ -125,6 +125,7 @@ export interface Text {
 export interface Parameter {
   type: "param";
   name: string;
+  pattern?: string;
 }
 
 /**
@@ -133,6 +134,7 @@ export interface Parameter {
 export interface Wildcard {
   type: "wildcard";
   name: string;
+  pattern?: string;
 }
 
 /**
@@ -228,6 +230,35 @@ export function parse(str: string, options: ParseOptions = {}): TokenData {
     return value;
   }
 
+  function pattern() {
+    let count = 1;
+    let value = "";
+
+    while (index < chars.length) {
+      const char = chars[index++];
+
+      if (char === "\\") {
+        value += char + chars[index++];
+        continue;
+      }
+
+      if (char === "(") {
+        count++;
+      } else if (char === ")") {
+        count--;
+        if (count === 0) break;
+      }
+
+      value += char;
+    }
+
+    if (count) {
+      throw new PathError(`Unbalanced pattern at index ${index}`, str);
+    }
+
+    return value;
+  }
+
   while (index < chars.length) {
     const value = chars[index];
     const type = SIMPLE_TOKENS[value];
@@ -240,6 +271,8 @@ export function parse(str: string, options: ParseOptions = {}): TokenData {
       tokens.push({ type: "param", index: index++, value: name() });
     } else if (value === "*") {
       tokens.push({ type: "wildcard", index: index++, value: name() });
+    } else if (value === "(") {
+      tokens.push({ type: "pattern", index: index++, value: pattern() });
     } else {
       tokens.push({ type: "char", index: index++, value });
     }
@@ -271,9 +304,13 @@ export function parse(str: string, options: ParseOptions = {}): TokenData {
       }
 
       if (token.type === "param" || token.type === "wildcard") {
+        const pattern =
+          tokens[pos].type === "pattern" ? tokens[pos++].value : undefined;
+
         output.push({
           type: token.type,
           name: token.value,
+          pattern,
         });
         continue;
       }
@@ -562,11 +599,12 @@ function toRegExpSource(
         );
       }
 
-      if (token.type === "param") {
-        result += `(${negate(delimiter, isSafeSegmentParam ? "" : backtrack)}+)`;
-      } else {
-        result += `([\\s\\S]+)`;
-      }
+      result += safePattern(
+        token,
+        delimiter,
+        isSafeSegmentParam ? "" : backtrack,
+        originalPath,
+      );
 
       keys.push(token);
       backtrack = "";
@@ -578,6 +616,33 @@ function toRegExpSource(
   return result;
 }
 
+/**
+ * Validate supported pattern characters.
+ */
+function safePattern(
+  token: Parameter | Wildcard,
+  delimiter: string,
+  backtrack: string,
+  originalPath: string | undefined,
+): string {
+  if (token.pattern !== undefined) {
+    if (!/^[a-zA-Z0-9\|]+$/.test(token.pattern)) {
+      throw new PathError(
+        `Unsupported pattern "${token.pattern}" for "${token.name}" ${token.type}`,
+        originalPath,
+      );
+    }
+
+    return `(${token.pattern})`;
+  }
+
+  if (token.type === "param") {
+    return `(${negate(delimiter, backtrack)}+)`;
+  }
+
+  return `([\\s\\S]+)`; // Wildcard (.+)
+}
+
 /**
  * Block backtracking on previous text and ignore delimiter string.
  */
@@ -618,12 +683,14 @@ function stringifyTokens(tokens: Token[]): string {
     }
 
     if (token.type === "param") {
-      value += `:${name(token.name)}`;
+      value +=
+        `:${name(token.name)}` + (token.pattern ? `(${token.pattern})` : "");
       continue;
     }
 
     if (token.type === "wildcard") {
-      value += `*${name(token.name)}`;
+      value +=
+        `*${name(token.name)}` + (token.pattern ? `(${token.pattern})` : "");
       continue;
     }