Cardiac autonomic function was evaluated in 23 patients with fibrocalculous pancreatic diabetes (FCPD). Though none of the patients had any symptoms referable to autonomic dysfunction, 5 had abnormal heart rate responses. The variability in the heart rate in response to deep breathing was the earliest abnormality found in our patients. Four of the 5 patients had clinical evidence of neuropathy while all 5 had retinopathy and overt nephropathy. We therefore conclude that the autonomic nervous system can be involved in patients with FCDP even as early as 2 years after the onset of the disease, and thus that evaluation of the autonomic nervous system should be part of the routine evaluation of all patients with FCPD.