Lectins recognizing D-galactosides were purified from the body wall of an echiuroid; Urechis unicinctus and two annelids; Neanthes japonica and Marphysa sanguinea, with single step lactosyl-agarose affinity column chromatography. SDS-PAGE under reduced and non-reduced conditions showed that U. unicinctus lectin had a major (36 kDa) and two minor (40 and 14 kDa) proteins, and that N. japonica lectin and M. sanguinea lectin had single 33 and 35 kDa proteins, respectively. Lectins were solubilized in the presence of lactose from tissues, and all polypeptides were shown to have sugar binding activity. The antisera raised against U. unicinctus lectin and N. japonica lectin crossreacted with each other but did not crossreact with bull frog (Rana catesbeiana) egg galectin-1 or a D-galactoside-specific lectin purified from sea urchin (Anthocidaris crassispina) eggs. These echiuroid and annelid lectins are immunologically similar, but distinct from members of the vertebrate galectin family.