The surface architecture of adult male Schistosoma mansoni was explored using a range of lectins with differing carbohydrate specificites. Highest specific binding was achieved with concanavalin A and the agglutinin of molecular weight 60000 from Ricinus communis; the binding of wheat germ agglutinin was mostly non-specific. Small amounts of peanut agglutinin and soybean agglutinin binding were observed and the binding of these lectins was increased by pre-treating the parasite with neuraminidase. The fucose binding protein of Lotus tetragonolobus failed to bind. These results indicate that mannose and/or glucose, galactose, N-acetylglucosamine, N-acetyl-galactosamine and sialic acid are exposed on the surface of the adult male schistosome.