This study was done to determine that vitamins I and C are synergistic in protecting liver cells during hepatic ischemia and repefusion. Rats treated with vitamins I and C were subjected to 60 min of hepatic ischemia and to 1 and 5 hr of reperfusion thereafter. Serum aminotransferase level and microsomal lipid peroxidation were markedly increased by ischemia/reperfusion. These increases were significantly attenuated by vitamins E, C or its combination. Hepatic wet weight-to-dry weight ratio was increased in ischemic group, but this increase was prevented by combination of vitamin I and C. Bile flow and cholate output were markedly decreased by ischemia/reperfusion and vitamin C alone and combination of vitamin I and C restored their secretion. Cytochrome P-450 content and aminopyrine N-demethylase activity were decreased by ischemia/ reperfusion and restored by vitamin C and combination of vitamin I and C to the level of sham-operated rat. Aniline p-hydroxylase activity was increased by ischemia/reperfusion and this increase was prevented by vitamin E. Our findings suggest that ischemia/reperfusion diminishes hepatic secretory and microsomal functions by increasing lipid peroxidation and vitamins I and C synergistically ameliorates these changes.