This study evaluated the mortality experience of 2384 workers at a plant in Colorado that produced aldrin, azodrin, vapona, and other pesticides. Subjects were followed up for a median of 29 years, from 1952 through 1990. Comparisons of the cohort’s mortality rates with those of the Colorado population indicated that observed and expected numbers of deaths were similar for all causes (465 observed/473 expected) and for all cancers (113/106). Standardized mortality ratios were elevated for hepatobiliary cancer (5/2.0; standardized mortality ratio, 249, 95% confidence interval, 81 to 581), due to an excess of biliary duct/gall bladder cancer, and for pneumonia (20/13; standardized mortality ratio, 150, 95% confidence interval, 92 to 232). These increases were limited to white men in hourly jobs but were not limited to any particular production unit and did not display duration-response trends. It is unlikely that these excesses are due to occupational exposures at the plant. © 1995, The American College of Occupational and Environmental Medicine.