Patients with effort angina and a history of cold intolerance performed brief submaximal exercise bicycle test in various temperatures with separation of inspiration and room air. Exposure to a cold room (-10 degrees C) and inhalation of very cold air(- 35 degrees C) in a normal room caused a significant decrease in maximal workload. Heart rate, systolic blood pressure, and rate-pressure product were significantly higher during exercise when compared with findings in the normal room. The decrease in maximal workload correlated significantly to the increase in heart rate and rate pressure product during exercise in both conditions, and to the increase in systolic blood pressure at exposure to a cold room. Exposure to 10 and 0 degree C environmental temperature and inhalation of moderately cold air (- 10 degrees C) did not cause any significant changes in maximal workload, heart rate, blood pressure, or rate pressure product during exercise, compared to the findings in the normal room. In conclusion, skin cooling seems to be far more important in its effect on heart load and the working capacity in patients with effort angina than inhalation of moderately cold air; inhalation of very cold air, however, does cause changes in working capacity similar to those of exposure to a cold environment. Increase in heart work during exercise is likely to cause the decrease in working capacity observed both with skin cooling and cold air inhalation.