In 1987, the National Institute for Occupational Safety and Health conducted a cross-sectional medical study to examine the long-term health effects of occupational exposure to chemicals and materials contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). This study compared living workers employed more than 15 years earlier in the production of sodium trichlorophenol (NaTCP), and 2,4,5-trichlorophenoxyacetic ester (2,4,5-T ester) with an unexposed comparison group. Health status of the worker and comparison populations was collected through a comprehensive set of standardized interviews and medical examinations. Lipid adjusted serum TCDD levels were also measured. Workers had a statistically significantly elevated mean serum lipid-adjusted TCDD level (workers = 220 pg per g of lipid [range = not detected-3,400 pg per g of lipid], and referents 7 pg per g of lipid [range not detected-20 pg per g of lipid], P < 0.001). Compared to a community-based referent population, the prevalence of chronic bronchitis, chronic obstructive pulmonary disease, peripheral neuropathy, depression, cardiovascular outcomes (myocardial infarction, angina, cardiac arrhythmias, hypertension, and abnormal peripheral arterial flow), abnormal porphyrin levels, and abnormal ventilatory function parameters FEV1.0, FVC, or FEV1.0/FVC% in workers, was not statistically significantly different. In contrast, relationships were observed between serum 2,3,7,8-TCDD levels and the enzyme gamma-glutamyltransferase (GGT), the reproductive hormones serum testosterone, luteinizing, and follicle-stimulating hormones, and abnormal high-density lipoprotein concentration, counts of CD3/Ta1 cells (helper lymphocytes), and fasting serum glucose levels. Current diagnosis of chloracne was associated with the highest levels of serum 2,3,7,8-TCDD. Analysis of other endpoints continues.