A clinical epidemiologic study was conducted to determine the long-term health effects of workplace exposure to the process of manufacturing the herbicide (2,4,5-trichlorophenoxy)acetic acid including contaminants such as 2,3,7,8-tetrachlorodibenzo-rho-dioxin. The population consisted of two cohorts: 204 clearly exposed and 163 not exposed. Among the exposed, clinical evidence of chloracne persisted in 55.7%. None of the not exposed experienced chloracne development. An association was found between the persistence of chloracne and the presence and severity of actinic elastosis of the skin. There is an association between exposure and the history of gastrointestinal tract ulcer. Pulmonary function values among those who were exposed and who currently smoked were lower than those who were not exposed and who currently smoked. The data assembled in the study indicate no evidence of increased risk for cardiovascular disease, hepatic disease, renal damage, or central or peripheral nervous system problems.