Until now a few serotypes of M-class I group A streptococci (GAS) have been shown to encode VirR, a positive regulatory factor for the coordinate expression of the M protein (emm) and C5a peptidase (scpA) genes. The polymerase chain reaction technique has been applied to the genomic template of 36 GAS serotypes to demonstrate the general presence of VirR (virR) genes and scpA in GAS of both M classes. A virR gene region conserved in size was demonstrated for every strain investigated. Differences between virR genes from GAS of the two M classes were mainly confined to the 3' end of the gene and a region upstream of the gene's promoter. Every M-class II strain and some M-class I isolates were shown to possess a scpA gene of 4.6 kb, the rest of the M-class I GAS harbors a 3.5-kb scpA gene. The additional segment of 1.1 kb in the large-size scpA genes was located within a region of direct repeats at the 3' end of the gene. Among the serotypes encoding a large-size scpA gene a minority exhibits additional sequence variation downstream of the region of direct repeats.