1. Rabbit antiserum to human whole saliva cross-reacts with both human serum and semen. After absorption of the antiserum by affinity chromatography on a column of immobilized serum protein, the cross-reactions with serum were eliminated.
2. The absorbed antiserum, however, still cross-reacted with semen thus indicating the presence of proteins with immunological similarity in both saliva and semen, but which did not occur in serum.
3. Some of these proteins clearly showed a reaction of complete immunological identity between saliva and semen.
4. The presence of the non-serum proteins in both saliva and semen might be related to common functions in both such as lubrication or antibacterial activity.