Six patients of terciary yaws, were treated with Penicillin in small dosis at Evandro Chagas Hospital of the Oswaldo Cruz Institute. The lesions presented by the patients were: gummatous ulcerations, periostitis, osteitis, osteoporosis and gangoza (rhinopharyngitis mutilans). In all cases, clinic recovery were obtained, the time of treatment varying from 2 to 8 months. The total amount of oxford units 'per" subject varied from 48.000 to 586.800 Patients with bone lesions, ever after the treatment, has not showed complete recomposition of the bone structure, ever so aparently healing and with negative sorologics tests. Identical results has been observed in patient showing the same lesions and treated with neo-arsphenamine. The patients are still under observations at the Hospital.