Interferon will be evaluated for its antineoplastic activity in the prevention and treatment of murine osteogenic sarcoma. The efficacy of interferon will be determined: (1) in tissue culture against a continuous line of osteogenic sarcoma cells derived from a 239 Pu-induced osteogenic sarcoma in C57B1/6 mice, (2) in an in vivo model utilizing osteogenic sarcoma tumor cells implanted subcutaneously into syngeneic mice, and (3) in lung metastases established by intravenous inoculation of the continuous line of osteogenic sarcoma cells. Based on the efficacy of these initial experiments, the capacity of interferon to prevent the induction of osteogenic sarcomas in mice exposed to 239 Pu will now be delineated and the treatment of established tumors will be attempted.