Our study is based on the examination of 2,000 aortic valves obtained from fresh cadavers (1,499 males, 501 females) at the Institute of Forensic Medicine in Rio de Janeiro. We discovered 13 valves having two leaflets, giving a prevalence of 0.65%, much lower than generally reported in the literature. All 13 valves were from males, 10 from whites, three from mulattos, and none from blacks. Special attention was given to the raphe and the leaflets, the calcification of which can lead to stenosis. The only valves with normal texture and flexibility were two obtained from children less than one year old. All the other valves were thickened, and five of them had some degree of calcification. Six valves were judged to be functioning normally, while 7 valves were abnormal, 5 being stenotic and two showing evidence of insufficiency. The insufficiency in one was due to endocarditis, but in the other was due to redundancy of the leaflets. The only other cardiac anomaly discovered in these 13 cases was one patient with aortic coarctation. Bifoliate aortic valve, therefore, is probably the most common cardiac anomaly, although its prevalence as discovered in Brazil is lower than that reported in the literature. It affects mainly white males. After the fourth decade of life, most valves present some thickening, with stenosis being the most common complication. As is well recognised, infective endocarditis and aortic insufficiency are the other frequent complications. It is in general, nonetheless, an isolated anomaly.