The inhibitory effect of three polyacetylene compounds, panaxydol, panaxynol and panaxytriol isolated from Panax ginseng C.A. Meyer on $CCl_4$induced lipid peroxidation in vivo and in vitro hepatic microsomal lipid peroxidation induced by ADP-$Fe^{3+}$, NADPH and NADPH-cytochrome P-450 reductase were investigated. Their effects on lowering the lipid peroxide levels both in serum and liver and lowering the serum enzyme (GOT, GPT, LDH) activities without the $CCl_4$-induction were also determined. Male ICR mice were pretreated i.p. with polyacetylene compounds or DL-${alpha}$-tocopherol before administration of $CCl_4$ i.p. and 20 hr after the administration of $CCl_4,$ serum and liver were analyzed. Hepatic microsome was isolated and used for the in vitro NADPH-dependent lipid peroxidation system. Except for panaxynol, treatment with polyacetylenes to control mice did not reduce the levels of lipid peroxides and serum enzyme activities. Panaxynol itself inhibited lipid peroxidation in the liver of normal mice. Polyacetylene compounds protected from the $CCl_4$-induced hepatic lipid peroxidation and lowered serum lipid peroxide levels. Polyacetylenes also inhibited the in virto hepatic microsomal lipid peroxidation in a dose-dependent manner. The results suggest that panaxydol, panaxynol and panaxytriol seem to be the antioxidant components which contribute the anti-aging activities of Panax ginseng C.A. Meyer.