The hypothalamo-pituitary-testicular axis was evaluated in a group of 23 men who worked in the lead smelting industry and had a history of occupational inorganic lead exposure. The endocrine status of the workers was related to lead poisoning biological markers. According to the duration of their lead exposure they were divided into three groups: group 1 less than 1 year, n = 5; group 2 between 3 and 5 years, n = 8; group 3 greater than 5 years, n = 10. Serum testosterone (T), steroid binding globulin (SBG), free testosterone index (T/SBG), serum luteinizing hormone (LH), follicle stimulating hormone (FSH), Blood lead levels, and blood zinc protoporphyrin (ZPP) were measured in all workers. Groups 2 and 3 showed a decrease in serum testosterone levels, an increase in SBG levels, and a decrease in T/SBG index, suggesting a correlation between testicular dysfunction and duration of exposure. There was an increase in serum LH in group 1, which was not progressive. This suggests that prolonged lead exposure initially produces a direct testicular toxicity followed by hypothalamic or pituitary disturbance when longer periods of exposure take place.