Vital status and cause of death were assessed for 232 of a group of 233 workers engaged in the manufacturing and formulation of aldrin, dieldrin, endrin and (for a limited period) Telodrin. This group is part of the total exposed population of more than 1000 workers and was selected for follow up on account of the high exposures in the initial years of manufacturing and formulation and of the long exposure (mean 11 years) and observation (mean 24 years) periods. Total observed mortality was 25 versus 38 expected on the basis of the death statistics of the male Dutch population. Of the 9 cancer deaths, 3 were caused by lung cancer, while the remaining 6 were each of a different nature. Although in this group exposures have been high and exposure, as well as observation periods, were long enough for meaningful evaluation, this study revealed no indication of a specific carcinogenic activity of aldrin, dieldrin or endrin in manufacturing plant workers exposed to these products.