The impact of supplemental handwriting and spelling instruction on learning to write was examined in an experimental study with first grade students who were not acquiring these skills as rapidly as their classmates. Thirty students (16 boys, 14 girls) were randomly assigned to a handwriting and spelling instructional condition or a phonological awareness instructional control condition. Students in each condition received 16 h of one-on-one instruction. The treatment condition was designed to improve children's handwriting fluency, handwriting legibility, spelling accuracy, and knowledge of spelling patterns. In comparison to students in the phonological awareness control condition, students who received supplemental handwriting and spelling instruction made greater gains in handwriting fluency, handwriting legibility, and spelling accuracy. The treatment condition also resulted in greater gains in sentence construction fluency and composition vocabulary, but did not statistically enhance composition length or composition quality. These findings provide partial support for the theoretical proposition that text transcription skills are causally related to writing. Further, this study demonstrates that explicit and supplemental handwriting and spelling instruction can play an important role in teaching writing to young children who acquire text transcription skills more slowly than their peers.