SUMMARYObjective: To compare clinical and bacteriologic responses to intramuscular benzathine penicillin G (BPG) and single dose of amoxicillin in Group A streptococcal (GAS) pharyngitis. Design: This study included 571 children from 6 to 15 years old age, with pharyngitis, who were admitted to 45 elementary and guidance schools from 7 regions of Education Organization in North-East of Iran, Mashhad. They were screened for enrollment and if he/she presented pharyngitis with clinical criteria of sore throat, erythema, exudate and tender or enlarged anterior cervical lymph nodes. Exclusion criteria included reports of antibiotic use, negative throat culture for GAS and history of allergy to the drugs. Clinical and bacteriologic responses to BPG and once daily orally amoxicillin were considered and compared. Results: In the amoxicillin group, treatment failure was more than the penicillin group (18.9% vs. 6.4%, respectively) but the difference was not statistically significant (p < 0.05). Both drugs were significantly effective in reducing pharyngitis manifestations but penicillin was significantly more effective in reducing exudate than amoxicillin. Conclusion: Our study was in line with studies comparing the two drugs. The results show that once-daily therapy with amoxicillin is as effective as intramuscular benzathine penicillin G for the treatment of GAS pharyngitis, but penicillin was significantly more effective in reducing exudate and concurrent signs vs. amoxicillin.