Effects of dietary cholesterol and taurine supplementation on hepatic total and phospholipid fatty acid compositions were evaluated in rats fed one of the following semisynthetic diets for 5 weeks : control diet(CD, cholesterol free and taurine free diet); high cholesterol diet(HCD, CD＋1.5% cho lesterol); high cholesterol, high taurine diet(HCHTD, HCD＋1.5% taurine). Diet induced changes in hepatic total fatty acid compositions were very similar to those in hepatic phospholipid fatty acid compositions. The HCD significantly decreased the percentage of total saturated fatty acids(SFA), and increased the percentage of total monounsaturated fatty acids(MUFA) of hepatic total lipids and phospholipids as compared to the values for the control rats(p<0.001). HCHTD significantly elevated the percentage of $Sigma$SFA and lowered the percentage of $Sigma$MUFA compared to the values for the HCD(p<0.001). Percentages of hepatic total and phospholipid 18:3$omega$3, 20:5$omega$3, 18:2$omega$6 and 20:3$omega$6 were significantly higher in rats fed the HCD than the values for the control rats, and the percentages of their elongation and desaturation products(22:5$omega$3, 22:6$omega$3, 20:4$omega$6, 22l:4$omega$6 and 22: 5$omega$6) were significantly lower in rats fed the HCD compared to those for the control rats. HCD significantly lowered the Δ5 desaturation(20:3$omega$6⇒20:4$omega$6) and Δ4 desaturation(22:4$omega$6⇒22:5$omega$6) indices, and the elongation index of $omega$3 fatty acid(20:5 $omega$3⇒22:5$omega$3) in rat liver. HCHTD reversed the cholesterol induced changes in the compositions of $omega$3 and $omega$6 fatty acids. These results suggest the possibility that dietary cholesterol and taurine supplementations affect plasma and liver lipid levels, at least in part, by changing the hepatic phospholipid fatty acid compositions and thereby modulating the physical characteristics of the membrane and the activities of microsomal enzymes involved in lipid metabolism.