The most common bacterial cause of tonsillopharyngitis is group A beta-hemolytic streptococci (GABHS) and penicillin is the drug of choice for the treatment of these infections. However, a disturbing trend toward penicillin failure has developed in some communities. It has been proposed that penicillin tolerance is a possible explanation for this failure. In this study, penicillin tolerance of GABHS strains isolated from 263 children with tonsillopharyngitis, was investigated between December 2000-March 2001. As a result, none of the isolated strains was found to be penicillin resistant or penicillin tolerant according to minimal inhibitory concentration and minimal bactericidal concentration values for penicillin G, determined by microdilution method.