Antitumor activity of the adduct between Carboplatin and α-cyclodextrin has been tested against Sarcoma 180 (S180) and Ehrlich ascites carcinoma (EAC) murine tumors. The preliminary toxicity has also been evaluated by histological examinations of the treated animals. The results show the adduct has less antitumor efficacy than and similar toxicity to Carboplatin.