When biannual phone calls revealed a participant death, staff attempted to collect death certificates, autopsy reports, relevant medical records, and interviews with attending physicians or eyewitnesses. An independent mortality and morbidity review board examined these data and classified causes of death. In addition, a National Death Index review provided date and cause of death for all U.S. study participants through the end of 2001. Vital status at 31 December 2001 or 14.5 years, whichever was earlier, was successfully determined for 98.3% of all participants; missing individuals were Canadians who had been lost to follow-up and were not accessible through the National Death Index. Mortality end points were classified in 7 categories: coronary heart disease, cardiovascular disease including coronary heart disease, lung cancer, other cancer, respiratory disease excluding lung cancer, other, and unknown. The “other” category included but was not limited to liver disease, kidney disease, sepsis, accidents, suicide, and AIDS.