The hemipenes of the Madagascan boas Acrantophis madagascariensis, A. dumerili, and Sanzinia madagascariensis are described in detail. All Boinae (sensu Underwood, 1976) have basically similar hemipenes. The Madagascan boas, and Candoia, however, share two variations (i, a vertical flounce with which the transverse flounces fuse, and which travels obliquely distad over and around the arms; ii, sulcal forks that do not extend to the tips of the arms) which are not found in other members of the Boinae.