Aclacinomycin (ACM) is an oncostatic of the anthracycline family, largely used in patients and experimentally in mice. ACM has been reported to enhance phagocytosis, secretion of free oxygen radicals and of interleukin 1. Its injection is also followed by an increase of the cytotoxic and cytostatic activity of murine peritoneal macrophages. In the present work we investigated whether ACM modifies the antigen-presenting cell capacity of murine peritoneal macrophages. Purified T lymphocytes were cultured with peritoneal macrophages from either normal or ACM treated mice (4 mg/kg day -4) which were previously incubated with phytohemagglutinin. The T cell proliferative response was greater in cultures with normal macrophages, indicating that macrophages from ACM-treated mice had a better antigen presenting activity than normal untreated macrophages.