Whole-cell protein profiles obtained by SDS-PAGE were used in conjunction with physiological tests to differentiate strains of Streptococcus canis isolated from dogs. Fermentation of trehalose and lactose, aesculin hydrolysis together with production of beta-D-glucuronidase and alpha-D-galactosidase allowed the demonstration of nine different biotypes. However, visual analysis of the protein patterns and comparison by the coefficient of Dice showed minor differences in band patterns among strains. Only two different profiles were observed. Although a correlation between biotyping and protein profile has been found, this kind of analysis did not provide the basis for a typing method.