The risk of ischemic heart disease (IHD) has been studied in relation to working conditions encountered in a primary aluminum smelter employing over 6,000 men. During the period 1975-1983, 306 new cases of IHD were identified which were matched with 575 referents. A logistic regression analysis was performed to adjust for differences in smoking habits, high blood pressure, hyperglycemia, hypercholesterol-emia, and obesity. Results from this showed that white collar workers had a significantly lower risk of IHD (odds ratio 0.47, 95% confidence interval 0.31-0.70). Among blue collar workers, a significantly higher risk was observed for workers in the reduction division of the plant (OR 1.72, CI 1.09-2.97) including, in particular, Soderberg (OR 1.71, CI 1.07-2.72) and prebake (OR 2.26, CI. 1.27-4.02) potroom workers. The risk of IHD did not increase with the length of time worked in these occupations. The search for associations (among blue collar workers) of risk with nine specific contaminants (benzene soluble material, fluoride, total dust, sulfur dioxide, carbon monoxide, thermal stress, noise, physical load, and mental load) proved inconclusive, with no association reaching statistical significance.