Fatty acid synthase (EC 2. 3. 1. 85; FAS) is reported as a potential new therapeutic target for the treatment of obesity. A total of 31 Chinese medicinal herbs used in weight-reducing prescriptions of traditional Chinese medicine were investigated for FAS inhibition. It was found that 17 of these herbs exhibited FAS inhibitor activity and nine were highly potent FAS inhibitors. The inhibitory potencies of the active components of Polygonum multiflorum (tuber fleeceflower) root, Loranthus parasiticus (parasitic loranthus), Camellia sinensis (green tea) leaf and Ginkgo biloba leaf were similar to or greater than cerulenin. The first three of these four herbs significantly reduced the body weight of rats on their oral administration. Moreover, P. multiflorum and L. parasiticus significantly reduced food intake in rats.