Forty-three 10th-grade boys and girls of upper-average intelligence were divided into two groups of poor and good writers (as determined by past performance, present teacher evaluation, and the evaluation by three experienced judges of two sets of sample compositions) to determine significant composition factors which could account for writing performance. Subjects wrote on expository composition as a regular class assignment, were questioned in a tape-recorded interview about their writing practices, and then were asked to register their attitudes toward 21 writing concepts on a 10-item adjective scale. A regression analysis combining scalar interview items and attitude dimension items confirmed a definitive relationship between writer type and the following factors: worth of ideas; self-rating as a writer; sense of purpose in writing; concern for organization; usefulness of ideas from the media of television, film, and radio; and initial sentence control. (Author/MF)