The high bone-Pb seen in retired workers can be explained by the long exposure periods, the higher exposure levels in earlier decades, and the slow excretion of lead accumulated in bone. The importance of the skeletal lead pool as an endogenous source of lead exposure in retired smelters was indicated by the associations between the B-Pb or U-Pb, on the one hand, and the bone-Pb, on the other. In active workers, the ongoing occupational exposure was dominant. The in vivo X-ray fluorescence technique is still mainly a research tool, and more work has to be done before it can be used more widely in clinical practice. However, over the next decade we can anticipate retrospective, prospective and cross-sectional epidemiological studies in which bone lead determinations reflecting the previous lead exposure in both occupationally and nonoccupationally lead exposed populations are related to various types of adverse health outcomes. Such studies will improve our knowledge of dose-response patterns and provide data that will have an impact on hygienic threshold limit values and prevention of lead-induced diseases.