The specificity of Moluccella laevis lectin was investigated by analysing its binding to glycosphingolipids separated on thin-layer chromatograms or adsorbed on microtitre wells. The binding activity of the lectin was highest for glycosphingolipids with terminal alpha-linked N-acetylgalactosamine, both in linear structures, as the Forssman glycosphingolipid, GalNAc alpha 3GalNAc beta 3Gal alpha 4Glc beta 1Cer, and in branched structures, as glycosphingolipids with the blood group A determinant, GalNAc alpha 3(Fuc alpha 2)Gal beta. In addition, the lectin bound, though considerably more weakly, to linear glycosphingolipids with terminal alpha-linked galactose. When considering the use of the M. laevis lectin for biochemical and medical purposes this cross-reactivity may be of importance.