diff --git a/docs/content/docs.md b/docs/content/docs.md
index 19e157be0..09f7ae0e0 100644
--- a/docs/content/docs.md
+++ b/docs/content/docs.md
@@ -192,6 +192,8 @@ Checks the files in the source and destination match.  It
 compares sizes and MD5SUMs and prints a report of files which
 don't match.  It doesn't alter the source or destination.
 
+`--size-only` may be used to only compare the sizes, not the MD5SUMs.
+
 ### rclone dedupe remote:path ###
 
 By default `dedup` interactively finds duplicate files and offers to
diff --git a/fs/operations.go b/fs/operations.go
index f320047e8..d2eb6e223 100644
--- a/fs/operations.go
+++ b/fs/operations.go
@@ -684,6 +684,33 @@ func MoveDir(fdst, fsrc Fs) error {
 	return nil
 }
 
+// checkIdentical checks to see if dst and src are identical
+//
+// it returns true if differences were found
+func checkIdentical(dst, src Object) bool {
+	Stats.Checking(src)
+	defer Stats.DoneChecking(src)
+	if src.Size() != dst.Size() {
+		Stats.Error()
+		ErrorLog(src, "Sizes differ")
+		return true
+	}
+	if !Config.SizeOnly {
+		same, _, err := CheckHashes(src, dst)
+		if err != nil {
+			// CheckHashes will log and count errors
+			return true
+		}
+		if !same {
+			Stats.Error()
+			ErrorLog(src, "Md5sums differ")
+			return true
+		}
+	}
+	Debug(src, "OK")
+	return false
+}
+
 // Check the files in fsrc and fdst according to Size and hash
 func Check(fdst, fsrc Fs) error {
 	differences := int32(0)
@@ -753,26 +780,9 @@ func Check(fdst, fsrc Fs) error {
 		go func() {
 			defer checkerWg.Done()
 			for check := range checks {
-				dst, src := check[0], check[1]
-				Stats.Checking(src)
-				if src.Size() != dst.Size() {
-					Stats.DoneChecking(src)
-					Stats.Error()
-					ErrorLog(src, "Sizes differ")
+				if checkIdentical(check[0], check[1]) {
 					atomic.AddInt32(&differences, 1)
-					continue
 				}
-				same, _, err := CheckHashes(src, dst)
-				Stats.DoneChecking(src)
-				if err != nil {
-					continue
-				}
-				if !same {
-					Stats.Error()
-					atomic.AddInt32(&differences, 1)
-					ErrorLog(src, "Md5sums differ")
-				}
-				Debug(src, "OK")
 			}
 		}()
 	}
diff --git a/fs/operations_test.go b/fs/operations_test.go
index 7b01d0830..6ddf92ec7 100644
--- a/fs/operations_test.go
+++ b/fs/operations_test.go
@@ -1003,8 +1003,13 @@ func TestCheck(t *testing.T) {
 	fstest.CheckItems(t, r.fremote, file1, file3)
 	check(3, 2)
 
-	r.WriteObject("potato2", "------------------------------------------------------------", t1)
-	fstest.CheckItems(t, r.fremote, file1, file2, file3)
+	file2r := file2
+	if fs.Config.SizeOnly {
+		file2r = r.WriteObject("potato2", "--Some-Differences-But-Size-Only-Is-Enabled-----------------", t1)
+	} else {
+		r.WriteObject("potato2", "------------------------------------------------------------", t1)
+	}
+	fstest.CheckItems(t, r.fremote, file1, file2r, file3)
 	check(4, 1)
 
 	r.WriteFile("empty space", "", t2)
@@ -1012,6 +1017,12 @@ func TestCheck(t *testing.T) {
 	check(5, 0)
 }
 
+func TestCheckSizeOnly(t *testing.T) {
+	fs.Config.SizeOnly = true
+	defer func() { fs.Config.SizeOnly = false }()
+	TestCheck(t)
+}
+
 func (r *Run) checkWithDuplicates(t *testing.T, items ...fstest.Item) {
 	objects, size, err := fs.Count(r.fremote)
 	if err != nil {