Previous studies showed that zinc deficiency influences the fatty acid composition of rat tissues, but the influence of dietary fat on the effects of zinc deficiency was not considered at that time. The present study was therefore conducted to investigate the effect of zinc deficiency on lipid concentrations in the liver and on fatty acid composition of liver phospholipids in rats fed diets containing coconut oil or fish oil, using a bifactorial experimental design. To ensure an adequate food intake all rats were force-fed. The zinc-deficient rats fed the coconut oil diet developed fatty livers, whereas zinc-deficient animals fed the fish oil diet did not. The zinc-deficient rats in both dietary fat groups had lower levels of linoleic acid, arachidonic acid and total (n-6) fatty acids in the liver phospholipids, especially in the phosphatidylcholine, but greater concentrations of (n-3) fatty acids compared with zinc-adequate controls. We conjecture that zinc deficiency influences incorporation of polyunsaturated fatty acids into phosphatidylcholine. The lower levels of arachidonic acid are replaced in the zinc-deficient animals fed a coconut oil diet by docosapentaenoic and docosahexaenoic acids and in the zinc-deficient animals fed a fish oil diet by eicosapentaenoic acid. The replacement of arachidonic acid by other fatty acids in the phospholipids is likely to have implications for prostaglandin synthesis. The study shows that the type of dietary fat influences the effects of zinc deficiency on fatty acid composition and especially on lipid concentrations in the liver.