The early effects of 4’-epidoxorubicin (Epi-Adriamycin) on liver regeneration and late effects on liver function were studied after a standard partial hepatectomy in rats. 4’-epidoxorubicin was given intravenously immediately preoperatively. Neither suppression nor delay in DNA synthesis (analyzed by incorporation of 3H-thymidine) during the first 72 h postoperatively was registered after a dose of 5 mg/kg body weight. Four weeks following the dose of 5 mg/kg a slight decrease was found in liver weight (8%), body weight (8%) and plasma albumin values (9 %) compared with the partial hepatectomized controls. Total protein, alkaline phosphatase, total bilirubin and alanine aminotransferase were not changed. A dose of 2 mg/kg did not alter any of the parameters. No histological signs of liver and kidney damage were seen. The results indicate that preoperative treatment with 4’-epidoxorubicin combined with partial hepatectomy may possibly be used in humans without clinically significant impairment of liver regeneration and function of the remaining liver and without histological detectable nephrotoxicity. The dosage of 4’-epidoxorubicin must, however, be adjusted according to species differences in pharmacok