Various aspects of the epidemiology of schistosomiasis mansoni werernstuoieo for a period of one year at Bahir Dar ~ith the primerno"bj ecti V0 of elucioating the transmission patterns.rnParasitological surveys revealed an overall prevalence of 12% amongrnresidents of Kebeles 8, 9 and 10. More males ( 17%) than femalesrn(8%) were infected ( P.(.O.Ol). The overall prevalence for schoolrnchildren of Dil chibo anO Sertse Dengel were 32% and 45%, respectively.rnSchool children yielded high annual incidence at the second surveyrn(February). Malacological findings suggested that Biomphalariarnpfeifferi snails peaked in density in September, towards the en6 ofrnthe rainy season in Lake Tana ana in January, around the miadle ofrnthe dry season at a site on the bank of the River Abay. InrnSeptember, infected snails were recovered from all collection sites.rnSchistosome infection also developed in a relatively large numberrnof mice immersed in the month of September. In two series ofrnsurveys, the major ~Iater contact activities were identified and itrnwas observed that there were diurnal and seasonal/variations inrnthese activities.rnThe study in general revealed that infection rates depend on age,rnsel< and geographical location with respect to wat er body. Snailrnpopulation dynamics and associated schistosomal infection seem torndepend on rainfall and associated ecological changes. Incidencernstudies, malacological findings and sentinel - mouse el