We compared the clinical and electrophysiological findings in seven patients with familial amyloid polyneuropathy (FAP) and six with hereditary sensory and autonomic neuropathy type I (HSAN). Both groups had progressive loss of pain and temperature appreciation, beginning distally in the feet. In HSAN, the median sensory nerve action potentials (SNAP) were lost early, but the sympathetic skin responses (SSR) were always preserved. In FAP, the SSR were lost at an early stage. The SSR may thus help to distinguish between these two causes of small‐fiber neuropathy early in the course of the disorder. © 1999 John Wiley & Sons, Inc. Muscle Nerve 22: 1283–1286, 1999