Group A Beta Haemolytic Streptococcus (GABHS) are the commonest cause of bacterial pharyngitis. GABHS Pharyngitis can be complicated by neck abscesses, glomerulonephritis, and rheumatic heart disease if the diagnosis is delayed. The Modified Centor score is an algorithm designed to predict the likelihood of streptococcal pharyngitis based on clinical features in relation to age of the patient. To determine the validity of the modified Centor score in diagnosing acute GABHS pharyngitis and to determine the antibiotic susceptibility profile of the GABHS isolates among patients with a sore throat attending Mulago National Referral Hospital. (MNRH) Of the 110 patients enrolled the overall prevalence of GABHS was 3.6%. The Modified centor score (McIsaac) had a sensitivity of 25%, a specificity of 23.6%, a positive and negative predictive values of 1.2% and 89.3% respectively, for the identification of GABHS pharyngitis. All GABHS isolates were susceptible to penicillin. The sensitivity of the GABHS isolates to erythromycin was 50%.