Objectives- Prompt diagnosis and appropriate treatment of streptococcal pharyngitis is essential for prevention of acute rheumatic fever (ARF) as the most dangerous complication of beta hemolytic group A streptococcus (Sb#HA) pharyngitis and the most common cause of acquired heart disease. As part of the National Project for Primary Prevention of Acute Rheumatic Fever (PPORF), this study was performed to determine the prevalence of Sb#HA pharyngitis, the healthy carrier rate and the MIC (minimum inhibitory concentration) and the MBC (minimum bactericidal concentration) of penicillin on streptococcus BHA Methods- This descriptive and cross-sectional survey studied more than 1000 students and patients aged 5-15 years, selected randomly for the determination of S,BHA pharyngitis prevalence and healthy carrier rate. Additionally, part of this research was experimental and interventional with the aim of determining the MIC and MBC of penicillin on S,b#HA, in the throat of patients and healthy carriers. Results- According to the results, 20% of all sore throats were streptococcal (S,b#HA), healthy carrier rate was 4.7%, penicillin MBC was 125-0.060 u/ml and penicillin MIC was 31.85-0.03 u/ml. Conclusion- Penicillin MBC and MIC in this study showed resistant streptococcal species in 15% and tolerant species in 11 % of cases (Iranian Heart Journal 2003; 4 (2,3): SS-58).