This study, undertaken to develop equations for predicting heat generated, involved testing nine men in treadmill, stepping, cranking, lifting, shoveling and handgripping tasks. The environmental temperatures were 26.7, 29.4 and 32.2 degrees centigrade (80, 85 and 90 Fahrenheit, respectively). Variables monitored were body weight, heart rate and pulmonary ventilation. A set of three equations predicting heat generated resulted. The effect of the weight variables was checked with eight overweight men exercising on a treadmill. The best of the equations could be used for normal weight subjects, but not for overweight ones.