An historical cohort mortality study of research and development personnel (primarily chemists) actively employed on Dec 31, 1961, with at least 1 year of service with the Allied Corporation was carried out. These employees experienced lower mortality for all causes of death combined and all cancer causes combined than would be expected on the basis of the general US population. The degree of deficit in all causes of death combined was below the healthy worker effect usually associated with occupational mortality studies of production workers. There was one statistically significsn t excess, that for cancer of the prostate among research laboratory personnel who worked during the period 1946 to 1966, a period during which researchers may have been exposed to insecticides or fluorine derivatives. Substantial deficits were observed for causes of death known to be related to life-style, suggesting that mortality among Allied's salaried employees, including research and development workers, may have been influenced more by these factors than by occupational factors.