The effects of dietary zinc on hepatic collagen and prolyl hydroxylase activity in normal and alcoholic rats has been investigated in four groups of pair-fed male Wistar rats given either liquid ethanol or a control diet for 12 wk. Each group of pair-fed animals received a diet with a different zinc concentration (standard diet, 7.6 mg/L; low-zinc diet, 3.4 mg/L; zinc-supplemented diet, 76 mg/L; and zinc-extrasupplemented, 300 mg/L. There were no significant differences in hepatic collagen concentration and prolyl hydroxylase activity between alcoholic and normal rats receiving a standard diet (collagen, 77 +/- 5 and 73 +/- 6 micrograms/mg protein; and prolyl hydroxylase; 37 +/- 26 and 36 +/- 22 cpm/mg protein). Alcoholic rats fed a low-zinc diet showed increased prolyl hydroxylase activity (75 +/- 10 cpm/mg protein, p less than 0.05), although no changes in hepatic collagen (77 +/- 10 micrograms/mg protein) were observed in comparison with rats fed a standard alcoholic diet. By contrast, hepatic collagen was significantly lower in alcoholic rats fed a zinc-supplemented diet (66 +/- 4 and 63 +/- 3 micrograms/mg protein, p less than 0.05 and p less than 0.01, respectively), and hepatic prolyl hydroxylase activity was particularly lower in rats receiving zinc 300 mg/L (18 +/- 20 cpm/mg protein). Similar effects were observed in normal rats. We conclude that dietary zinc influences hepatic prolyl hydroxylase activity and collagen deposition in alcoholic rats, and in consequence, the control of dietary zinc is necessary to assess the effects of alcohol on collagen metabolism in rats.