Mastering sentence-construction skills is essential to learning to write. Limited sentence-construction skills may hinder a writer's ability to translate ideas into text. It may also inhibit or interfere with other composing processes, as developing writers must devote considerable cognitive effort to sentence construction. The authors examined whether instruction designed to improve sentence-construction skills was beneficial for more and less skilled 4th-grade writers. In comparison with peers receiving grammar instruction, students in the experimental treatment condition became more adept at combining simpler sentences into more complex sentences. For the experimental students, the sentence-combining skills produced improved story writing as well as the use of these skills when revising.