Early identification of children at risk of reading and writing difficulties is important for prevention and the provision of proper intervention before failure sets in. This thesis addresses the issue in the Tanzanian context, where many children in primary schools face reading and writing problems. This is evidenced in the high repetition anr dropout rates and poor school attendance of children. Many children complete primary education without the skills of reading and writing. The children remain unidentified for many reasons, amongst them a lack of proper screening instruments for identification. The aim of this study was to create and validate a theoretically founded group-based screening tool in Kiswahili for identifying first graders at risk of reading and writing difficulties. The role of certain home- and school-related factors for the children's reading and writing ability was also analyzed. The created screen was shown to have high reliability. Of 337 children screened in Morogoro Municipality, Tanzania, 24% were found to be at risk of reading and writing difficulties and in need of special attention. These children obtained very low scores on all the tasks designed to measure letter identification, word identification, phonological awareness and spelling. These components are known to be sensitive predictors of reading in alphabetic languages, including transparent orthographies like Kiswahili. The screen also identified a group of children who are struggling, but who can manage with a little support. Many overaged school beginners seem to belong to the at-risk group. Of the home factors, the number of books at home explained 38% of the variance in reading and writing ability. Parents' reading ability and the support children get at home were also strong factors. Of the school-related factors, school attendance was critical, explaining 21% of the variance. Nursery school experience was also important. The study emphasizes that action is needed to support homes and schools in the process of improving school attendance. The screening instrument is considered effective for identifying children at risk of reading and writing difficulties. In addition to the original version, a short version is also presented. Both versions are easy to administer in a short time and do not require special orientation. The screen can be used by teachers as well as parents.