This study of S. haematobium infection in communities associated with irrigated schemes shows that prevalence rates are unusually high in adults, especially in men; and distribution disease is probably associated with at least the following three factors: (i) distance of the place of residence from the main transmission sites (ii) the dynamics of transmission in the waterbody and (iii) the human/water contact and contamination patterns. During this chemotherapy trial, at the first survey, only a little more than half (57.47%) of the people recorded in the census was present. Five visits of the survey team were necessary to obtain a compliance rate of 80.51% of the entire population. The indifference of the local people to seek diagnosis and treatment increased with succeeding surveys. It is only, during a subsequent treatment survey, carried out during the season of low agricultural activity and following an official written convocation, that a compliance rate similar to that of the first survey was recorded. If treatment is not given immediately after diagnosis as many as a fifth of positive cases do not appear for treatment. Oltipraz and praziquantel were administered. Their effectiveness could not be truly compared as there was a time lag of six months separating the administration of the treatments. However, based on the results of this trial both drugs gave good results especially in egg output intensity. But, a decrease of this parameter was also observed in non treated people. Seasonal variations of egg output or decrease of transmission could be involved.