We studied gender-related differences in the effect of a single dose of ethanol (EtOH) on liver regeneration following partial hepatectomy in male and female rats by determining polyamines and their related enzymes. When rats were orally treated with EtOH at 3 g/kg 1 hr before partial hepatectomy, liver ornithine decarboxylase (ODC) activity at 4 hr post-hepatectomy was found to be lower in EtOH-treated female than male rats (51% vs. 42%, P < 0.01). Although no EtOH effect was observed on spermidine acetyltransferase (SAT) activity, female rats showed significantly higher values than male rats. Among intra-hepatic polyamines, putrescine was strongly affected by EtOH and significantly reduced in both male and female rats, but the effect was more marked in female than in male rats (88% vs. 51%, P < 0.01). With respect to spermidine and spermine, male rats were unaffected by EtOH, whereas EtOH-treated female rats had lower levels. The gender-related differences became more distinct in terms of total polyamine; the decrease in total polyamine due to EtOH was observed in female rats only. These results suggested that there was a gender-related difference in the effect of EtOH on liver regeneration after partial hepatectomy, with the variations in polyamines probably affecting the subsequent process of liver regeneration.