A total of 98 isolates of group A streptococci of T1M1 serotype isolated in Finland during 1988-1995 from bacteremic, pharyngeal, and pyogenic infections were studied by molecular means. The typing techniques used included restriction endonuclease analysis, ribotyping, and random amplified polymorphic DNA analysis. Representatives of each observed genotype were also examined for carriage of the speA gene encoding for pyrogenic exotoxin A. All of the serotype T1M1 isolates studied were considered to be of a single clonal origin, and 66% were identical by all three genotyping techniques used. Among the remaining 34% of closely related isolates, 13 different genotypes were detected. All isolates studied carried the speA gene. No evidence was found of correlation of the genomic type to the severity of the infection or the time of isolation.