The process approach to writing instruction is one of the most popular methods for teaching writing. The authors conducted meta-analysis of 29 experimental and quasi-experimental studies conducted with students in Grades 1-12 to examine if process writing instruction improves the quality of students' writing and motivation to write. For students in general education classes, process writing instruction resulted in a statistically significant, but relatively modest improvement in the overall quality of writing (average weighted effect size [ES] = 0.34). Variation in ES was not related to grade, reliability of the writing quality measure, professional development, genre assessed, or quality of study. The process writing approach neither resulted in a statistically significant improvement in students' motivation nor enhanced the quality of struggling writers' compositions. (Contains 2 tables.)