The aim of the presents study is to investigate and compare the antioxidative effects and qualities of the cultivating root of Cynanchum Wilfori, which is increasingly used in recent days, with those of the wilding root, which has mainly been used in the past in oriental medicine for a tonic and also for prevention and treatment of various geriatric diseases including aging progress. For comparison of their antioxidative effects, the activities of the total extracts on lipid peroxidation and the activity of aldehyde oxidase(EC 1.2.3.1) as well as xanthine oxidase(EC 1.2.3.2) were investigated in vitro. In addition, their inhibitory effects on the activity of 5-lipoxygenase, which is known to induce inflammation and concerned with free radicals, were also determined in vitro. Furthermore, the amino acid contents of both roots were analyzed in order to compare their qualities. The results are as follows: 1. The wilding root inhibited significantly the activity of 5-lipoxygenase, showing five times more portent than the cultivating root. 2. Both of the wilding root and the cultivating root inhibited aldehyde oxidase activity in a dose-dependant manner. The wilding root was more effective than the other. 3. Both of the wilding root and the cultivating root dose-dependently suppressed lipid peroxidation in rat brain, kidney, and liver. 4. The anti-peroxidative effects of both roots appeared to be most strong in brain and least in liver. In particular, the cultivating root exhibited a significant inhibition on brain lipid peroxidation. 5. The cultivating root contained 15 amino acids including five essential amino acids in contrast with the less contents in the wilding root.