This is the final report on mortality amongst men in the WHO cooperative trial of the prevention of ischaemic heart disease (IHD) by clofibrate and it takes the follow-up a further 4 years to the end of 1982. Mean observation was 13.2 years, 5.3 in the trial and 7.9 afterwards. 1788 deaths were recorded in 208 000 man-years. In the 877 new deaths reported here, there was an excess of 9 deaths in the high cholesterol control group compared with the clofibrate-treated group. In the whole period there were 70 (11%) more deaths in the clofibrate-treated group. Excess mortality in the clofibrate-treated group was much greater during the "treatment period" (there was an excess of 47% during treatment compared with 5% after treatment had ended) and was due to a wide variety of causes other than IHD. Thus, the excess mortality in the clofibrate-treated group has not continued after the end of treatment. The substantial excess previously reported remains unexplained.