A prospective mortality study was conducted of the 800 employees who worked 3 months or more during the period January 1946 through June 1985, in the only plant in the US where the termiticide chlordane has been produced. The study covers the entire period of chlordane production to date and includes 7,347 person-years of employment at the chlordane plant and 21,585.5 person-years of follow-up since commencement of employment. All but three former employees considered to be alive at the end of the study period were either contacted directly or were identified as alive by a variety of reliable sources. Death certificates were obtained for 161 of the 181 decedents and reliable causes of death were reported for an additional 11 cases.Overall death rate was slightly less than expected but not to the level of statistical significance. Production workers with higher pesticide blood levels had lower standardized mortality ratios for cancer than nonproduction employees, and there appears to be an inverse relationship of cancer mortality to length of employment. An unexplained excess of cerebrovascular deaths was observed, offset by a lesser degree of cardiovascular deaths.