Tributyltin chloride (TBTC) is well known for its immunotoxic effect, in particular towards immature thymocytes. TBTC is also known to induce adipocyte differentiation in primary human bone marrow cultures, which is reflected in the decrease in a number of adipocyte-derived cytokines, chemokines and the adipocyte-linked hormone leptin. Since adipocytes influence haematopoiesis and lymphopoiesis for instance by these cytokines and hormones, we here investigated whether TBTC has an effect on specific lymphocyte subsets in human bone marrow primary cultures. FACS analysis showed a reduction of CD19/CD22-positive B cells by TBTC, both in the presence or absence of cytokines. The treatment did not cause a toxic effect on mature CD3+CD4+ and CD3+CD8+ T cells, suggesting selective TBTC toxicity on B lymphocytes in the presently used in vitro system.