Streptococcal diseases, namely, acute glomerulonephritis and acute rheumatic fever, are common features in the aboriginal population of the Northern Territory of Australia. We examined the group A streptococcal M types identified during various surveys conducted since 1987. Streptococci were predominantly isolated from skin infections. A high proportion of the isolates could not be serotyped by conventional means and were designated M nontypeable (MNT). M-specific DNA sequences from the MNT isolates were examined, and sequence types were proposed for the classification of MNTs. This allowed a more precise estimate of the M types present in a population study.