Tropaeolum tuberosum is an edible-tuber-producing cultigen of the Andes mountains. Historical beliefs relating to the effects of this species on human reproductive potential continue to the present day. T. tuberosum subsp. tuberosum contains p-methoxybenzylglucosinolate as its major secondary metabolite. The putative anti-aphrodisiac activity of T. tuberosum was examined in male rats fed a diet containing tubers of this taxon. Experimental animals and controls showed equal capability in impregnating females, although animals fed T. tuberosum showed a 45% drop in their blood levels of testosterone/dihydrotestosterone. This decrease appears to be related to the presence of isothiocyanates in the tubers. Feeding studies of female guinea pigs and in vitro studies to test the 17 beta-estradiol binding inhibition of plant extracts and of pure isothiocyanates failed to substantiate any estrogenic activity of these taxa. However, preliminary results suggest that N, N-di-(methoxy-4-benzyl)thiourea competitively inhibits estradiol binding and may have estrogenic activity. The antibiotic, insecticidal, nematocidal and diuretic properties of isothiocyanates substantiate several of the uses of T. tuberosum in Andean folk medicine.