The study will be a single blinded, randomized, controlled open label non-inferiority phase III, trial with two parallel groups, conducted in Ghana and Papua New Guinea (PNG). The ultimate goal is to establish if a 20mg/kg dose of azithromycin is as effective as a 30mg/kg dose in the treatment of yaws. Approximately 600 clinically and serologically diagnosed yaws patients will be included in the study. Patients will be randomized to receive treatment with the two antibiotic regimens as follow: (i) Regimen I (AZT20): Single oral dose of 20 mg/kg azithromycin (ii) Regimen II (AZT30): Single oral dose of 30 mg/kg azithromycin. The follow-up period of patients will be 6 months. Assessments before, during and after the antibiotic treatment will include full medical history, clinical assessment of the lesion and, laboratory investigations. The primary efficacy parameters are healing of the lesion at 4 weeks and a four-fold decline in RPR titre at 6 months after start of treatment.