The authors studied noncancer mortality among phenoxyacid herbicide and chlorophenol production workers and sprayers included in an international study comprising 36 cohorts from 12 countries followed from 1939 to 1992. Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin or higher chlorinated dioxins (TCDD/HCD) was discerned from job records and company questionnaires with validation by biologic and environmental measures. Standard mortality ratio analyses suggested a moderate healthy worker effect for all circulatory diseases, especially ischemic heart disease, among both those exposed and those not exposed to TCDD/HCD. In Poisson regression analyses, exposure to TCDD/HCD was not associated with increased mortality from cerebrovascular disease. However, an increased risk for circulatory disease, especially ischemic heart disease (rate ratio [RR] 1.67, 95% confidence interval [Cl] 1.23-2.26) and possibly diabetes (RR 2.25, 95% Cl 0.53-9.50), was present among TCDD/HCD-exposed workers. Risks tended to be higher 10 to 19 years after first exposure and for those exposed for a duration of 10 to 19 years. Mortality from suicide was comparable to that for the general population for all workers exposed to herbicides or chlorophenols and was associated with short latency and duration of exposure. More refined investigations of the ischemic heart disease and TCDD/HCD exposure association are warranted.