Three lectins, designated as Sg₁, Sg₂ and Sg₃, were identified in the serum of the desert locust Schistocerca gregaria. With the use of (NH₄)₂SO₄ fractionation, ion-exchange chromatography on DEAE-cellulose and affinity chromatography on CNBr-activated Sepharose 4B, three pools, each containing one of the putative lectins, were obtained. IEF, native PAGE and SDS/PAGE revealed that the three pools contained Sg₁, Sg₂ and Sg₃, respectively, with pI = 6.39, 8.11 and 6.8; native PAGE Rm = 0.44, 0.32 and 0.32; SDS/ PAGE subunits approximate molecular weights = 21.5, 44.5, and 43.9 kDa, respectively. Under reducing conditions, SDS/PAGE has separated each of Sg₂ and Sg₃ into two bands that indicate the presence of covalent interactions between their subunits, which are not present in Sg₁. The three lectins are more highly specific for rabbit RBCs than for those of other vertebrates. The HA of lectins are Ca² -dependent, heat-labile, and are inhibited strongly by α-linked-D-galactosides, followed by L-( )-rhamnose.