In 31 patients with coronary artery disease (autonomic neuropathy, n = 11; diabetes without neuropathy, n = 10; silent myocardial ischemia without diabetes, n = 10) difference in somatic pain threshold and plethysmographically determined reactive hyperemia induced by forearm skeletal muscle ischemia was investigated. There was no difference in reactive hyperemia after passive maximum forearm ischemia in the three groups indicating identical vascular reactivity. After symptom-limited ischemic work however, reactive hyperemia was significantly higher in patients with silent myocardial ischemia as compared to diabetic patients. Exercise time was longer in patients with silent myocardial ischemia (153 +/- 51 s) as in patients with diabetic neuropathy (139 +/- 45 s) and diabetics without neuropathy (120 +/- 45 s). Pain as a cause of termination of symptom-limited ischemic forearm exercise occurred less frequently in patients with diabetic neuropathy (2/11) and patients with silent myocardial ischemia (3/10) as compared to patients with diabetes without neuropathy (9/10). In conclusion, patients with silent myocardial ischemia have a higher ischemic tolerance in the working forearm as compared to diabetic patients with and without neuropathy. There is a quantitative difference in ischemic tolerance between patients with silent myocardial ischemia and patients with diabetic neuropathy.