A pilot study was conducted in Morelos, Mexico in March 1999 to assess the body burden of lead in 24 Mexican women of childbearing age. Lead levels were measured in whole blood and at three bone sites: two primarily trabecular (calcaneus and patella) and one primarily cortical (tibia). Demographic and reproductive characteristics of the women and potential sources of lead exposure were gathered by a direct interview. An inverse relationship was noted between months of lactation and age-adjusted calcaneus lead level (P = 0.001). No association was observed between age-adjusted patella or tibia lead level and months of lactation (P = 0.15). Blood lead levels were positively associated with the use of lead-glazed ceramics (P = 0.01). Bone and blood lead levels were observed to be 77% higher in these rural Mexican women than in urban New York City women. This pilot study provides further limited evidence for the hypothesis that lead mobilization occurs during lactation.