A comprehensive panel of immune parameters was evaluated among 145 lead-exposed workers with a median blood lead level (BLL) of 39 micrograms/dL (range: 15-55 micrograms/dL) and 84 unexposed workers. After adjusting for covariates, we found no major differences in the percentage of CD3+ cells, CD4+ T cells, CD8+ T cells, B cells, or NK cells between lead-exposed and unexposed workers, although the association between lead exposure and the number of CD4+ T cells was modified by age. We also found no differences between exposed and unexposed workers in serum immunoglobulin levels, salivary IgA, C3 complement levels, or lymphoproliferative responses. However, among exposed workers, the percentage and number of B cells were positively associated with current BLL, serum IgG was negatively associated with cumulative lead exposure, and the percentage and number of CD4+/CD45RA+ cells were positively associated with cumulative lead exposure. We found no evidence of a marked immunotoxic effect of lead at the exposure levels studied, although some subtle differences in immunologic parameters were noted.