AbstractA comparison was made of the proportional frequencies of deaths from ischemic heart disease (IHD) in Icelandic males of different occupational classes—farmers, seamen, laborers, craftsmen, and white‐collar workers. The study was based on the examination of death certificates for adult males for the period 1951–60. There was no evidence of significant differences in method of death certification or in diagnostic transfer.At ages 35–64 the ratio of IHD deaths to all deaths ranged from 10.4 per cent for farmers to 30.4 per cent for white‐collar workers. In between were seamen and laborers on the lower side and craftsmen on the upper side of the over‐all value, which was 20.1 per cent. At ages 75 and older there were practically no differences. Further analysis indicated an essentially similar occupational pattern with respect to mortality rates, except for a somewhat contracted range. The rates for white‐collar workers, nevertheless, were about twice as high as for the farmers.The difference in IHD mortality between farmers and white‐collar workers at least, could not be related to the amounts or composition of dietary fats, but there was evidence of an association with physical activity and overnutrition. So far this is compatible with the view that habitual positive energy balance may be more important as a risk factor for ischemic heart disease than is richness of t