diff --git a/PIL/PpmImagePlugin.py b/PIL/PpmImagePlugin.py
index 9aa5b1135..070efd185 100644
--- a/PIL/PpmImagePlugin.py
+++ b/PIL/PpmImagePlugin.py
@@ -63,7 +63,11 @@ class PpmImageFile(ImageFile.ImageFile):
             c = self.fp.read(1)
             if not c or c in b_whitespace:
                 break
+            if c > b'\x79':
+                raise ValueError("Expected ASCII value, found binary")
             s = s + c
+            if (len(s) > 9):
+                raise ValueError("Expected int, got > 9 digits")
         return s
 
     def _open(self):
@@ -96,7 +100,18 @@ class PpmImageFile(ImageFile.ImageFile):
                 ysize = s
                 if mode == "1":
                     break
-
+            elif ix == 2:
+                # maxgrey
+                if s > 255:
+                    if not mode == 'L':
+                        raise ValueError("Too many colors for band: %s" %s)
+                    if s < 2**16:
+                        self.mode = 'I'
+                        rawmode = 'I;16B'
+                    else:
+                        self.mode = 'I';
+                        rawmode = 'I;32B'
+                        
         self.size = xsize, ysize
         self.tile = [("raw",
                      (0, 0, xsize, ysize),
@@ -116,6 +131,11 @@ def _save(im, fp, filename):
         rawmode, head = "1;I", b"P4"
     elif im.mode == "L":
         rawmode, head = "L", b"P5"
+    elif im.mode == "I":
+        if im.getextrema()[1] < 2**16:
+            rawmode, head = "I;16B", b"P5"
+        else:
+            rawmode, head = "I;32B", b"P5"
     elif im.mode == "RGB":
         rawmode, head = "RGB", b"P6"
     elif im.mode == "RGBA":
@@ -123,8 +143,15 @@ def _save(im, fp, filename):
     else:
         raise IOError("cannot write mode %s as PPM" % im.mode)
     fp.write(head + ("\n%d %d\n" % im.size).encode('ascii'))
-    if head != b"P4":
+    if head == b"P6":
         fp.write(b"255\n")
+    if head == b"P5":
+        if rawmode == "L":
+            fp.write(b"255\n")
+        elif rawmode == "I;16B":
+            fp.write(b"65535\n")
+        elif rawmode == "I;32B":
+            fp.write(b"2147483648\n")
     ImageFile._save(im, fp, [("raw", (0,0)+im.size, 0, (rawmode, 0, 1))])
 
     # ALTERNATIVE: save via builtin debug function
diff --git a/Tests/images/16_bit_binary.pgm b/Tests/images/16_bit_binary.pgm
new file mode 100644
index 000000000..fd41a5c3d
Binary files /dev/null and b/Tests/images/16_bit_binary.pgm differ
diff --git a/Tests/images/16_bit_binary_pgm.png b/Tests/images/16_bit_binary_pgm.png
new file mode 100644
index 000000000..918be1ad4
Binary files /dev/null and b/Tests/images/16_bit_binary_pgm.png differ
diff --git a/Tests/test_file_ppm.py b/Tests/test_file_ppm.py
index fccb94905..34136a83c 100644
--- a/Tests/test_file_ppm.py
+++ b/Tests/test_file_ppm.py
@@ -12,3 +12,25 @@ def test_sanity():
     assert_equal(im.mode, "RGB")
     assert_equal(im.size, (128, 128))
     assert_equal(im.format, "PPM")
+
+def test_16bit_pgm():
+    im = Image.open('Tests/images/16_bit_binary.pgm')
+    im.load()
+    assert_equal(im.mode, 'I')
+    assert_equal(im.size, (20,100))
+
+    tgt = Image.open('Tests/images/16_bit_binary_pgm.png')
+    assert_image_equal(im, tgt)
+
+
+def test_16bit_pgm_write():
+    im = Image.open('Tests/images/16_bit_binary.pgm')
+    im.load()
+
+    f = tempfile('temp.pgm')
+    assert_no_exception(lambda: im.save(f, 'PPM'))
+
+    reloaded = Image.open(f)
+    assert_image_equal(im, reloaded)
+
+