The cells of 28 strains of the Lactobacillus acidophilus group were evaluated for hemagglutination (HA) activity. The activity was found in the surface layer (SL) protein fraction extracted by 2 M guanidine hydrochloride. The most SL proteins from the A group strains (L. acidophilus (A1), L. crispatus (A2), L. amylovorus (A3), and L. gallinarum (A4)) showed HA activity, but the proteins from the B group strains (L. gasseri (B1) and L. johnsonii (B2)) showed no activity. The SL proteins from the A group strains were composed in common of a main component having molecular mass of about 40-45 kDa on SDS-PAGE. The SL proteins from JCM 1034 strain that showed the highest HA activity was fractionated by CM-Toyopearl ion-exchange chromatography. The highest HA activity was detected in the major protein of 41 kDa. This protein was purified and shown to be composed of about 50% of hydrophobic amino acids. The HA activity of the protein (1034 lectin) was specifically inhibited by fetuin and bovine lactoferrin at the concentrations of 80 and 160 micrograms/ml, respectively. The removal of N-acetylneuraminic acid from fetuin significantly decreased the inhibitory activity.