This study investigated the effectiveness of Modified Cognitive Strategy Instruction in Writing (CSIW) with mildly mentally retarded students' skills in writing problem/solution texts. Participants were from two self-contained and multiage classrooms in Turkey. Instruction had a positive impact on the amount of time students spent planning and writing problem/solution texts. There was also an increase in text length, elements, coherence, and quality of students' compositions. These effects were maintained over time. (Contains 1 table and 1 figure.)