diff --git a/.changeset/silent-cooks-visit.md b/.changeset/silent-cooks-visit.md
new file mode 100644
index 0000000..de156c4
--- /dev/null
+++ b/.changeset/silent-cooks-visit.md
@@ -0,0 +1,5 @@
+---
+'dataloader': minor
+---
+
+Set default maximum batching size to 500 to prevent Denial of Service.
diff --git a/README.md b/README.md
index 664a043..5b8adcd 100644
--- a/README.md
+++ b/README.md
@@ -395,7 +395,7 @@ Create a new `DataLoader` given a batch loading function and options.
 | Option Key        | Type     | Default                                   | Description                                                                                                                                                                                |
 | ----------------- | -------- | ----------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
 | `batch`           | Boolean  | `true`                                    | Set to `false` to disable batching, invoking `batchLoadFn` with a single load key. This is equivalent to setting `maxBatchSize` to `1`.                                                    |
-| `maxBatchSize`    | Number   | `Infinity`                                | Limits the number of items that get passed in to the `batchLoadFn`. May be set to `1` to disable batching.                                                                                 |
+| `maxBatchSize`    | Number   | `500`                                | Limits the number of items that get passed in to the `batchLoadFn`. May be set to `1` to disable batching.                                                                                 |
 | `batchScheduleFn` | Function | See [Batch scheduling](#batch-scheduling) | A function to schedule the later execution of a batch. The function is expected to call the provided callback in the immediate future.                                                     |
 | `cache`           | Boolean  | `true`                                    | Set to `false` to disable memoization caching, creating a new Promise and new key in the `batchLoadFn` for every load of the same key. This is equivalent to setting `cacheMap` to `null`. |
 | `cacheKeyFn`      | Function | `key => key`                              | Produces cache key for a given load key. Useful when objects are keys and two objects should be considered equivalent.                                                                     |
diff --git a/src/index.d.ts b/src/index.d.ts
index 136ad88..ee7dae0 100644
--- a/src/index.d.ts
+++ b/src/index.d.ts
@@ -95,7 +95,7 @@ declare namespace DataLoader {
     batch?: boolean;
 
     /**
-     * Default `Infinity`. Limits the number of items that get passed in to the
+     * Default `500`. Limits the number of items that get passed in to the
      * `batchLoadFn`. May be set to `1` to disable batching.
      */
     maxBatchSize?: number;
diff --git a/src/index.js b/src/index.js
index 997d85a..a58ceae 100644
--- a/src/index.js
+++ b/src/index.js
@@ -412,7 +412,7 @@ function getValidMaxBatchSize(options: ?Options<any, any, any>): number {
   }
   const maxBatchSize = options && options.maxBatchSize;
   if (maxBatchSize === undefined) {
-    return Infinity;
+    return 500;
   }
   if (typeof maxBatchSize !== 'number' || maxBatchSize < 1) {
     throw new TypeError(