4'-O-tetrahydropyranyl adriamycin (THP-ADM) is a newly synthetized anthracyclin reported to be an efficient oncostatic drug in animals and in humans and which is less cardiotoxic than adriamycin (ADM). Since part of the efficiency of anthracyclins may be due to their immunoregulatory activity, we investigated to what extent THP-ADM had such properties and we observed that THP-ADM stimulates free oxygen radical secretion by murine peritoneal macrophages. They could thus help the control of infections cancer patients have a tendency to develop. Peritoneal macrophages of THP-ADM-treated mice have an in vitro cytostatic activity towards P815 tumor cells higher than normal cells and when stimulated with LPS they secrete more IL-1, an important effector of the immune response.