ABSTRACT: A study was made in Bahir Dar, north-western Ethiopia, for a period of twelve months, to determine the incidence of schistosomiasis mansoni. All children aged 10 year:. and younger in Dil Chibo and Teyima Elementary Schools were stool-examined by the formal-ether concentration technique at the beginning of the study to select schistosomiasis mansoni negative children for a later incidence study. Accordingly, 139 children in Dil Chibo and 104 children in Teyima were found negative and used for an incidence study. In the incidence surveys, the stool specimens were examined by the Kato method. The overall annual1ncidence rates for Dil Chibo and Teyima school children were 194/1000 and 382/1000, respectively. The rates obtained at the second survey were higher than the rates obtained at the first survey, 164/1000 and 36/1000, respectively, for Dil Chibo and 292/1000 and 77/1000, respectively, for Teyima schools, Males had a higher schistosomiasis incidence than females (P<0.01), The incidence also appeared to vary with age. The value of incidence as a measure of transmission is discussed. [Ethiop.J. Health Dev. 1993; 7 (1):17-20]