Ischemic pain threshold and tolerance levels using the tourniquet pain technique and electrical cutaneous pain thresholds were measured in patients with asymptomatic ischemie heart disease. Thirty asymptomatic patients, who repeatedly exhibited no angina pectoris pain during the occurrence of exercise-induced coronary ischemia (⩾ 0.1 mV ST segment depression in exercise ECG) were compared to 30 randomly selected symptomatic control patients. In a smaller patient group (6 symptomatic, 6 asympatomatic) the degree of forearm ischemia during the tourniquet test was determined non-invasively by monitoring transcutaneous pO₂. Results indicated that asymptomatic patients needed significantly more time to reach pain threshold following occlusion of forearm blood flow and exhibited significantly lower tcpO₂ values at threshold than symptomatic patients. Electrical pain thresholds were also elevated in the asymptomatic group. These findings indicate that the phenomenon of asymptomatic myocardial ischemia can be explained by an extracardiac pain modifying mechanism.