Human erythrocyte specific lectin was isolated from the seeds ofErythrina variegata Linn. var.orientalis Linn. Merrill. The lectin preferentially agglutinated erythrocytes in the sequence of O>B>A = AB. The lectin was purified 19-fold by affinity chromatography on acid treated sepharose 4B with an yield of 81%. The purified lectin was found homogeneous on polyacrylamide gel electrophoresis. The erythroagglutination reaction was inhibited by N-acetyl-D-galactosamine, D-galactose and lactose at very low concentration. The haemagglutination by the purified lectin was not inhibited by different hexose and pentose sugars even at high concentration. The purified lectin was a glycoprotein and agglutinated leucocytes at 3 μg protein concentration. The lectin induced transformation of peripheral blood lymphocytes in cultures.