Human and bovine group B streptococcus (GBS) isolates were serotyped and amounts of released N-acetylneuraminic acid from N-acetylneuraminyl-lactose by extracellular neuraminidase were colorimetrically assessed. According to serotyping by co-agglutination method, 30 of bovine GBS and 43 of human GBS could be serotyped (ST) by monospecific antisera coated with protein A. The remaining GBS strains were designated as nontypeable (NT). The released N-acetylneuraminic acid was determined in 90.9% of bovine GBS and 47.1% of human GBS isolates. The differences between the total bovine and human GBS isolates were statistically significant (p < 0.001). In comparison with detected N-acetylneuraminic acid level in bovine and human groups, significant decrease was observed in the bovine NT group according to increased human NT (p < 0.01) and bovine ST groups (p < 0.01). However, N-acetylneuraminic acid level in bovine ST and bovine total groups significantly (p < 0.001) increased with respect to the human ST group and human total group. Neuraminidase activity was detected more frequently in bovine GBS isolates. Considerable differentiations were observed between typeable and nontypeable isolates.