The relationship between blood lead (B-Pb) indices and bone lead was determined in 81 smelter workers. Lead exposure had changed dramatically since the smelter opened 27 years ago; therefore, workers were stratified by years employed. Seventy workers, hired prior to 1979 (Group 1), had a mean (range) age of 46 years (35-64), mean years of employment 23 (16-27), mean years of education 8 (0-13), mean B-Pb 26 micrograms dl-1 (13-43), mean time-weighted average (TWA) B-Pb 44 micrograms dl-1 (23-57) and mean integrated blood lead index (IBL), 983 micrograms Pb year dl-1 (537-1437). Eleven workers, hired after 1978 (Group 2), had a mean age of 34 years (24-55), mean years of employment 11 (5-14), mean years of education 11 (8-12), mean B-Pb 26 micrograms dl-1 (8-13), mean TWA 33 micrograms dl-1 (17-44) and mean IBL 378 micrograms year dl-1 (81-555). Bone lead measured in the mid-tibia used K-X-ray fluorescence. Mean bone lead in Group 1 and Group 2 was 45 (-7-90) and 11 (-12-33) micrograms Pb (g bone mineral)-1, respectively. Linear regression analysis demonstrated a significant relationship between bone lead and B-Pb indices. B-Pb accounted for 10.8%, years employed 12.7%, TWA 31.4% and IBL 36% of the bone lead variance. Using a previously established relationship, the mean bone lead predicted a mean B-Pb content of approximately 8 micrograms dl-1 in Group 1 as compared to 2 micrograms dl-1 in Group 2. The mean B-Pb was 26 micrograms dl-1 in both groups despite differences in contribution from bone stores. Differential contribution of ambient air lead to B-Pb in the two groups of current workers with similar job titles may reflect use of personal protective equipment.