The classical techniques of M protein and opacity factor (OF) typing and T agglutination typing remain the "gold standard" in identifying group A streptococci, although newer techniques have been proposed to assist laboratory scientists, microbiologists, epidemiologists and clinicians in the precise identification and characterisation of these organisms. Because of the current scarcity of M-typing sera and the increased use by many laboratories of T typing as the sole method of group A identification, a table is presented to indicate specific correlation between the T-agglutination pattern and the M serotype. The use of this table will enable not only more selective use of typing sera but also, perhaps, result in improved understanding and ultimately in correlating these defined patterns with newer and more sensitive techniques.