A gene from Streptococcus pneumoniae was cloned in lambda EMBL301 and then expressed in Escherichia coli, which cleaved the fluorogenic neuraminidase substrate 2'-(4-methylumbelliferyl)-alpha-d-N-acetylneuraminic acid. The cloned gene therefore encodes an enzyme with neuraminidase activity. On the basis of restriction mapping and DNA hybridization studies, this gene could be distinguished from another pneumococcal neuraminidase gene cloned previously (A. M. Berry, J. C. Paton, E. M. Glare, D. Hansman, and D. E. A. Catcheside, Gene 71:299-305, 1988). Both neuraminidase genes were found in each of five isolates, covering at least three serotypes, of pneumococci tested.