The antibiotic activities of extracts of Gnetum paniculatum and G. schwackeanum and of substance isolated from the latter plant, namely resveratrol, gnetin C and gnetin E were tested against several bacteria and fungi. The extract and all the substances isolated from Gnetum schwackeanum were active toward S. aureus, S. apidermis and M. smegamatis. Gnetin C and resveratrol showed activity against C. albicans but only gnetin C was active toward C. parapsilosis and S. cerevisiae.