diff --git a/src/future/http/HTTPSFuture.php b/src/future/http/HTTPSFuture.php
--- a/src/future/http/HTTPSFuture.php
+++ b/src/future/http/HTTPSFuture.php
@@ -22,6 +22,10 @@
   private $rawBodyPos = 0;
   private $fileHandle;
 
+  private $downloadPath;
+  private $downloadHandle;
+  private $parser;
+
   /**
    * Create a temp file containing an SSL cert, and use it for this session.
    *
@@ -137,6 +141,19 @@
     }
   }
 
+  public function setDownloadPath($download_path) {
+    $this->downloadPath = $download_path;
+
+    if (Filesystem::pathExists($download_path)) {
+      throw new Exception(
+        pht(
+          'Specified download path "%s" already exists, refusing to '.
+          'overwrite.'));
+    }
+
+    return $this;
+  }
+
   /**
    * Attach a file to the request.
    *
@@ -174,6 +191,12 @@
     $uri = $this->getURI();
     $domain = id(new PhutilURI($uri))->getDomain();
 
+    $is_download = $this->isDownload();
+
+    // See T13396. For now, use the streaming response parser only if we're
+    // downloading the response to disk.
+    $use_streaming_parser = (bool)$is_download;
+
     if (!$this->handle) {
       $uri_object = new PhutilURI($uri);
       $proxy = PhutilHTTPEngineExtension::buildHTTPProxyURI($uri_object);
@@ -364,6 +387,27 @@
       if ($proxy) {
         curl_setopt($curl, CURLOPT_PROXY, (string)$proxy);
       }
+
+      if ($is_download) {
+        $this->downloadHandle = @fopen($this->downloadPath, 'wb+');
+        if (!$this->downloadHandle) {
+          throw new Exception(
+            pht(
+              'Failed to open filesystem path "%s" for writing.',
+              $this->downloadPath));
+        }
+      }
+
+      if ($use_streaming_parser) {
+        $streaming_parser = id(new PhutilHTTPResponseParser())
+          ->setFollowLocationHeaders($this->getFollowLocation());
+
+        if ($this->downloadHandle) {
+          $streaming_parser->setWriteHandle($this->downloadHandle);
+        }
+
+        $this->parser = $streaming_parser;
+      }
     } else {
       $curl = $this->handle;
 
@@ -416,6 +460,21 @@
       $body = null;
       $headers = array();
       $this->result = array($status, $body, $headers);
+    } else if ($this->parser) {
+      $streaming_parser = $this->parser;
+      try {
+        $responses = $streaming_parser->getResponses();
+        $final_response = last($responses);
+        $result = array(
+          $final_response->getStatus(),
+          $final_response->getBody(),
+          $final_response->getHeaders(),
+        );
+      } catch (HTTPFutureParseResponseStatus $ex) {
+        $result = array($ex, null, array());
+      }
+
+      $this->result = $result;
     } else {
       // cURL returns headers of all redirects, we strip all but the final one.
       $redirects = curl_getinfo($curl, CURLINFO_REDIRECT_COUNT);
@@ -432,6 +491,14 @@
       self::$pool[$domain][] = $curl;
     }
 
+    if ($is_download) {
+      if ($this->downloadHandle) {
+        fflush($this->downloadHandle);
+        fclose($this->downloadHandle);
+        $this->downloadHandle = null;
+      }
+    }
+
     $profiler = PhutilServiceProfiler::getInstance();
     $profiler->endServiceCall($this->profilerCallID, array());
 
@@ -444,7 +511,12 @@
    * the data to a buffer.
    */
   public function didReceiveDataCallback($handle, $data) {
-    $this->responseBuffer .= $data;
+    if ($this->parser) {
+      $this->parser->readBytes($data);
+    } else {
+      $this->responseBuffer .= $data;
+    }
+
     return strlen($data);
   }
 
@@ -460,6 +532,20 @@
    * @return string Response data, if available.
    */
   public function read() {
+    if ($this->isDownload()) {
+      throw new Exception(
+        pht(
+          'You can not read the result buffer while streaming results '.
+          'to disk: there is no in-memory buffer to read.'));
+    }
+
+    if ($this->parser) {
+      throw new Exception(
+        pht(
+          'Streaming reads are not currently supported by the streaming '.
+          'parser.'));
+    }
+
     $result = substr($this->responseBuffer, $this->responseBufferPos);
     $this->responseBufferPos = strlen($this->responseBuffer);
     return $result;
@@ -473,6 +559,20 @@
    * @return this
    */
   public function discardBuffers() {
+    if ($this->isDownload()) {
+      throw new Exception(
+        pht(
+          'You can not discard the result buffer while streaming results '.
+          'to disk: there is no in-memory buffer to discard.'));
+    }
+
+    if ($this->parser) {
+      throw new Exception(
+        pht(
+          'Buffer discards are not currently supported by the streaming '.
+          'parser.'));
+    }
+
     $this->responseBuffer = '';
     $this->responseBufferPos = 0;
     return $this;
@@ -690,5 +790,8 @@
     return true;
   }
 
+  private function isDownload() {
+   return ($this->downloadPath !== null);
+  }
 
 }
diff --git a/src/parser/http/PhutilHTTPResponse.php b/src/parser/http/PhutilHTTPResponse.php
--- a/src/parser/http/PhutilHTTPResponse.php
+++ b/src/parser/http/PhutilHTTPResponse.php
@@ -6,6 +6,7 @@
   private $headers = array();
   private $body;
   private $status;
+  private $writeHandle;
 
   public function __construct() {
     $this->body = new PhutilRope();
@@ -30,11 +31,32 @@
   }
 
   public function appendBody($bytes) {
-    $this->body->append($bytes);
+    if ($this->writeHandle !== null) {
+      $result = @fwrite($this->writeHandle, $bytes);
+      if ($result !== strlen($bytes)) {
+        throw new Exception(
+          pht('Failed to write response to disk. (Maybe the disk is full?)'));
+      }
+    } else {
+      $this->body->append($bytes);
+    }
   }
 
   public function getBody() {
+    if ($this->writeHandle !== null) {
+      return null;
+    }
+
     return $this->body->getAsString();
   }
 
+  public function setWriteHandle($write_handle) {
+    $this->writeHandle = $write_handle;
+    return $this;
+  }
+
+  public function getWriteHandle() {
+    return $this->writeHandle;
+  }
+
 }
diff --git a/src/parser/http/PhutilHTTPResponseParser.php b/src/parser/http/PhutilHTTPResponseParser.php
--- a/src/parser/http/PhutilHTTPResponseParser.php
+++ b/src/parser/http/PhutilHTTPResponseParser.php
@@ -7,6 +7,7 @@
   private $response;
   private $buffer;
   private $state = 'headers';
+  private $writeHandle;
 
   public function setFollowLocationHeaders($follow_location_headers) {
     $this->followLocationHeaders = $follow_location_headers;
@@ -17,6 +18,15 @@
     return $this->followLocationHeaders;
   }
 
+  public function setWriteHandle($write_handle) {
+    $this->writeHandle = $write_handle;
+    return $this;
+  }
+
+  public function getWriteHandle() {
+    return $this->writeHandle;
+  }
+
   public function readBytes($bytes) {
     if ($this->state == 'discard') {
       return $this;
@@ -90,7 +100,7 @@
             HTTPFutureParseResponseStatus::ERROR_MALFORMED_RESPONSE,
             $raw_headers);
 
-          $this->newHTTPRepsonse()
+          $this->newHTTPResponse()
             ->setStatus($malformed);
 
           $this->buffer = '';
@@ -166,6 +176,12 @@
 
   private function newHTTPResponse() {
     $response = new PhutilHTTPResponse();
+
+    $write_handle = $this->getWriteHandle();
+    if ($write_handle) {
+      $response->setWriteHandle($write_handle);
+    }
+
     $this->responses[] = $response;
     $this->response = $response;
     return $response;