The analysis and interpretation of skeletal lead is relatively common in anthropological research employing chemical analyses of human tissues. To provide an additional dimension to such research, this paper presents the rationale for, and a case study illustrating the use of skeletal lead isotope data to address problems of group affinity. The radiogenic origin of three of the four stable lead isotopes give lead from any given geologic deposit (source) a characteristic isotopic ''signature''. As lead does not fractionate measurably in biological systems, including human metabolism, the isotopic composition of skeletal lead reflects the source(s) of lead to which individuals were exposed. It is assumed that different cultural groups will be exposed to different sources of lead through natural processes and cultural practices. Given this assumption, lead isotope analysis of eight unidentified skeletons (two Native North Americans and six Fur Traders) from a 19th century fur trade cemetery was conducted. The results indicate that, as predicted, the Native North American and Fur Trader skeletal remains have different skeletal lead isotopic compositions. The differences are generally congruent with the two primary sources of lead available. (C) 1996 Academic Press Limited