The primary objective of the study is to compare the clinical efficacy of 5 days (800 mg x 4) versus 10 days (1000 mg x 3) treatment with phenoxymethylpenicillin (PcV) in adults, adolescents and children with streptococcal tonsillitis. Patients are recruited from 17 primary Health care centres in the south of Sweden. Adult men and women, youth and children ≥ 6 years of age who are visiting the primary Health care for sore throat with suspected tonsillitis and meeting the criteria in accordance with current treatment recommendations for pharyngotonsillitis, ie 3-4 Centor criteria (fever≥ 38.5, tender lymph nodes, coatings of the tonsils and absence of cough) and a positive rapid antigen detection test (RADT) for Group A streptococcus (GAS) will be included in the study. Patients will be randomized to be prescribed PcV of 5 and 10 days. Each patient or guardian fills daily in a short diary including aches, fever, PcV doses, pain relievers, adverse events etc. Five to seven days after last intake of PcV the general practioner make a clinical judgement if the patient has recovered from the pharyngotonsillitis. Questions to be asked are if remaining symptoms or new symptoms of sore throat is present, if adverse events have been noted or of any extra physician visits have been made. Throat swab for semi quantitative cultures of Streptococcus group A, C and G are made at randomization and five to seven days after last intake of PcV. A study nurse will contact the patients one month and three months after the last treatment day for follow-up. If the patient has reconsulted or been hospitalised for a sore throat or possible complication, those patient records will be examined.