Soluble beta-galactoside-specific lectins have been detected in many rabbits tissues and are relatively abundant in certain organs. These lectins are apparently identical to the lectin in rabbit bone marrow, which may be involved in inter-erythroblast associations during differentiation, and are very similar in structure and activity to lectins described in a number of species both in adult and embryonic tissues. The rabbit lectin is a monomer with a relative molecular mass of approximately 12 000 and has a low specific activity in the haemagglutination of trypsinized rabbit erythrocytes relative to lectins from other species, which are predominantly dimeric. In addition to the major antigen two minor isoforms of the rabbit galaptin were detected in all tissues. Since these lectins are widely distributed, it seems probable that they are involved in cellular functions that are prominent during development and also maintained in certain differentiated tissues. Experimental evidence currently available suggests that these lectins may be involved in the organization of extracellular matrix components.