diff --git a/docs/changelog.rst b/docs/changelog.rst
index dde53b23..0578ba07 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -27,6 +27,7 @@ In progress (unreleased)
 * :gh:issue:`1424` tests: Parameterize connection benchmarks
 * :gh:issue:`1424` tests: Standardise output of connection benchmarks
 * :gh:issue:`1424` tests: Parameterize throughput benchmark
+* :gh:issue:`1424` tests: Parameterize large message benchmark
 
 
 v0.3.37 (2026-01-08)
diff --git a/tests/bench/large_messages.py b/tests/bench/large_messages.py
index 8593a33a..7f4aea01 100644
--- a/tests/bench/large_messages.py
+++ b/tests/bench/large_messages.py
@@ -1,4 +1,4 @@
-# Verify _receive_one() quadratic behaviour fixed.
+'Measure throughput of messages.'
 
 import mitogen
 import mitogen.core
@@ -6,20 +6,27 @@ import mitogen.core
 
 @mitogen.main()
 def main(router):
-    c = router.fork()
+    import optparse
+    parser = optparse.OptionParser(description=__doc__)
+    parser.add_option(
+        '-i', '--iterations', type=int, metavar='N', default=10,
+        help='Number of iterations (default %default)')
+    parser.add_option('--debug', action='store_true')
+    opts, args = parser.parse_args()
+
+    c = router.fork(debug=opts.debug)
 
     n = 1048576 * 127
     s = ' ' * n
-    print('bytes in %.2fMiB string...' % (n/1048576.0),)
 
     t0 = mitogen.core.now()
-    for x in range(10):
+    for x in range(opts.iterations):
         tt0 = mitogen.core.now()
         assert n == c.call(len, s)
-        print('took %dms' % (1000 * (mitogen.core.now() - tt0),))
+
     t1 = mitogen.core.now()
-    print('total %dms / %dms avg / %.2fMiB/sec' % (
-        1000 * (t1 - t0),
-        (1000 * (t1 - t0)) / (x + 1),
-        ((n * (x + 1)) / (t1 - t0)) / 1048576.0,
-    ))
+    mean = (t1 - t0) / opts.iterations
+    transferred_size = n * opts.iterations
+    transfer_rate = transferred_size / (t1 - t0)
+    print('++ iterations %d, mean %.03f ms, rate %.03f MiB/s'
+          % (opts.iterations, 1e3 * mean, transfer_rate / 2**20))