The CAMP reaction is a synergistic lysis of erythrocytes by the interaction of an extracellular protein (CAMP factor) produced by some streptococcal species with the Staphylococcus aureussphingomyelinase C (beta-toxin). Group A streptococci (GAS [Streptococcus pyogenes]) have been long considered CAMP negative, and this reaction commonly has been used to distinguish GAS from Streptococcus agalactiae. We here provide evidence that GAS possess this gene and produce an extracellular CAMP factor capable of participating in a positive CAMP reaction. The S. pyogenes CAMP factor is specified by a 774-bp open reading frame homologous to the CAMP factor genes from S. agalactiae andStreptococcus uberis. This gene, designatedcfa, was isolated on a 1,256-bp fragment and cloned inEscherichia coli. Recombinant clones of E. coliexpressing cfa secreted an active CAMP factor. The deduced 28.5-kDa protein encoded by cfa consists of 257 amino acids, with a predicted 28-amino-acid signal peptide. Thecfa gene is widely spread among GAS: 82 of 100 clinical GAS isolates produced a positive CAMP reaction. Of the CAMP-negative strains, 17 of the 18 GAS strains contained the cfa gene. Additionally, CAMP activity was detected in streptococci from serogroups C, M, P, R, and U. The cfa gene was cloned and actively expressed in Escherichia coli and gene fusions were made, placing the β-galactosidase gene (lacZ) under control of the cfa promoter. These cfapromoter-lacZ fusions were introduced into S. pyogenes via a bacteriophage-derived site-specific integration vector where they showed that the cfa gene has a strong promoter that may be subject to as-yet-unidentified regulatory factors. The results presented here, along with previous reports, indicate that the CAMP factor gene is fairly widespread among streptococci, being present at least in groups A, B, C, G, M, P, R, and U.