In this study, I examined the effects of instruction in sentence combining on three measures of student writing : 1.) syntactic fluency; 2.) overall writing quality; and 3.) sentence -combining ability. Sentence combining is a method of writing instruction in which students rewrite a series of sentences into one syntactically more complex sentence. Two teachers instructed experimental group one (37 students) in sentence combining applied to revision. The same two teachers also instructed experimental group two (37 students) in sentence combining alone. A third teacher instructed the control students (38 students) in the standard ninth-grade English curriculum. To examine syntactic fluency, I analyzed students' writing for words per T-unit, clauses per T-unit, and words per clause. To examine overall writing quality, two trained raters assessed students' writing using forced choice holistic scoring. I also assessed students' sentence-combining ability. On syntactic fluency, the control group demonstrated statistically significant gains for mean number of words per clause. On overall writing quality, the control group also demonstrated statistically significant gains. On sentence-combining ability, both experimental group one and experimental group two demonstrated statistically significant gains. While the results do not support the first two research questions, on sentence-combining ability, the results suggest that ninth-grade writers can be taught sentence combining in a four-week, intensive instructional unit. Additionally, results suggest links between rhetorical and psychological theories and writing. However, the limitations of the results also suggest further sentence-combining research.