We studied the effects of alanine and glutamine administration on the inhibition of liver regeneration by acute ethanol treatment after partial hepatectomy (PH) in rats. When rats were dosed i.p. with ethanol at 2 g/kg at the time of PH, DNA synthesis 48 hr after PH was significantly inhibited, but it was completely reversed by the combined use of alanine and glutamine. Although hepatic ornithine decarboxylase (ODC) activity in the alcohol-treated group 4 hr after PH was significantly inhibited, there was a tendency towards recovery of the ODC inhibition in the alanine and glutamine-treated group. The putrescine (PUT) level in liver which was decreased by ethanol was also increased by the administration of alanine and glutamine. However, the levels of spermidine (SPD) and spermine (SPM) in liver were unaffected either by ethanol or by alanine and glutamine. These results suggest that alanine and glutamine show a protective effect on the inhibition of liver regeneration caused by acute ethanol treatment by improving polyamine metabolism, particularly by increasing hepatic PUT levels.