Seventeen persons, from 2 to 78 years of age, with clinical, epidemiological,immunological and parasitological diagnosis of american tegumentary leishmaniasis, were studied. All came from the endemic area of Jacarepaguá, a suburb of the city of Rio de Janeiro. The patients were treated with n-methylglucanine antimonate, using a dosage of 60 mg/kg/day, in three series of ten days duration each series, with intervals of ten days between each series, venous blood samples having been taken for the indirect immunefluorescent tests (IF-IgG) before, during and after medication. The seventeen individuals were reactive to the intradermal reaction of Montenegro (= 5 mm) and serum-reactive (= 1:45 mm) to the IF-IgG test; Leishmania b. braziliensis ssp was demonstrated or isolated in six cases (31.7%). Before treatment, the IF-IgG test showed positive in 76.4% of the cases (13 cases with titers = 1:90). The geometric averages of the reciprocal titer were as follows: before the first antimonial series (89,9); during treatment (63.6 to 29.3) and 10, 30 and 120 days after medication which revealed a clearly decreasing scale (14.9; 2.1 and 1.2), respectively. All lesions were healed upon termination of treatment, the scarring being most evident after the second series. Only 120 days after therapy were titers lower than 1:45 in all patients (16 cases - 94.1%). This suggests that, when the IF-IgG test is used as a control of cures, serological follow up is necessary during a minimum of three to four months.