diff --git a/source/index.ts b/source/index.ts
index 3ae4dd1..47727a4 100644
--- a/source/index.ts
+++ b/source/index.ts
@@ -135,10 +135,13 @@ namespace is { // tslint:disable-line:no-namespace
 	export const symbol = isOfType<Symbol>('symbol');
 	// tslint:enable:variable-name
 
+	export const nullOrUndefined = (value: any): value is null | undefined => null_(value) || undefined(value);
+	export const numericString = (value: any): value is String =>
+		!Number.isNaN(Number(value)) && !nullOrUndefined(value);
+
 	export const array = Array.isArray;
 	export const buffer = isBuffer;
 
-	export const nullOrUndefined = (value: any): value is null | undefined => null_(value) || undefined(value);
 	export const object = (value: any): value is object => !nullOrUndefined(value) && (function_(value) || isObject(value));
 	export const iterable = (value: any): value is IterableIterator<any> => !nullOrUndefined(value) && function_(value[Symbol.iterator]);
 	export const asyncIterable = (value: any): value is AsyncIterableIterator<any> => !nullOrUndefined(value) && function_(value[Symbol.asyncIterator]);
diff --git a/source/tests/test.ts b/source/tests/test.ts
index 66c3c9e..1199430 100644
--- a/source/tests/test.ts
+++ b/source/tests/test.ts
@@ -426,6 +426,14 @@ test('is.symbol', t => {
 	testType(t, 'symbol');
 });
 
+test('is.numericString', t => {
+	t.true(m.numericString('5'));
+	t.true(m.numericString('-3.2'));
+	t.true(m.numericString('Infinity'));
+	t.false(m.numericString(undefined));
+	t.false(m.numericString(null));
+});
+
 test('is.array', t => {
 	testType(t, 'array', ['emptyArray']);
 });