A comparative study on the evolutive morbidity of schistosomiasis mansoni in treated and non-treatd patients in an endemic area was carried-out with evalution of the treatment after one and six years. In the first uear after treatment there was both an improvement in the clinical conditions and a dramatic reduction in the number of S. mansoni eggs eliminated by the treated patients in relation to the controls. However, after six years of observations, although the number of S. mansoni eggs eliminated by the treated patients was still less than in the control group, it was nearly the same number as before treatment. in both treated and non-treated groups there was an increase in the severity of the clinical forms of schistosomiasis, with a certain tenency of greater severity in the control group. Therefore the authors recommend that the specific treatment of the population in endemic area should be done at intervals of two to three years, and that the treatment should be associated to the environmental sanitation, water supply and the education of the population.
schistosomiasis; evolution; Brazil