Blood specimens for dioxin congener analysis and clinical laboratory studies were recently obtained for 138 employees who had been potentially exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) following a 1953 trichlorophenol autoclave accident. Results for 34 clinical tests were regressed on three exposure measures (current TCDD concentration, log TCDD concentration back-calculated to the time of exposure, and chloracne status). Age, smoking status and body-mass-index were included as additional explanatory factors in the analyses. Positive associations were found between each of the exposure measures and both serum thyroxine (T4) and thyroxine binding globulin (TBG). Additional exposure-response associations were detected relative to several immune system parameters, erythrocyte sedimentation rate, platelet count and serum alkaline phosphatase. These data will be specifically helpful in interpreting the results of additional morbidity and mortality studies conducted within the same target population.