Differences in glucose intolerance within various occupational groups, i.e. laborers, clerks, and managers, and the related environmental factors were studied in ca. 9000 male workers of a certain factory. Age-and weight-adjusted prevalence rates of glucose intolerance were 3.2% in the laborers, 5.8% in the clerks, and 9.3% in the managers. In the managers, the total intake of calories was excessive for the amount of exercise expended; food intake was relatively low in complex carbohydrates and high in animal fats. The clerks were characterized by a high sugar intake. The low prevalence of glucose intolerance in the laborers was ascribed to the greater amount of exercise. Assigned work hours, however, probably affected the prevalence of diabetes in the laborers, which was 2.1% in subjects who worked all three shifts, but 0.9% in subjects working only day shifts. Thirty laborers from all 3 shifts consented to give urine specimens during their working time (8 hr), after the same amount of food and exercise in all of them. Urinary excretion of HGH and VMA during the midnight shift was significantly higher (p less than 0.05) than that during the day shift although urinary 170HCS was significantly low (p less than 0.01) at midnight. There were no significant changes in urinary CPR excretion between day and night shifts. These data indicate the importance of environmental factors, such as exercise, nutrition and stress, in glucose intolerance.