'Poly-plat', SSP and SAP are second generation analogs of cisplatin which have been shown to activate murine peritoneal macrophages in vivo and in vitro. Murine peritoneal macrophages treated with 'poly-plat', SSP or SAP (5 microg/mg) for 2 h are stimulated to form cytoplasmic extensions. Drug-treated macrophages also elicit an increase in the number of lysosomes. In addition, analysis of tissue culture supernatants shows increased levels of interleukin-1alpha and tumor necrosis factor-alpha. These results show that 'poly-plat', SSP and SAP enhance the immune system with greater efficacy and potency than cisplatin.