This research project was carried out to test the hypothesis that symbolic logic instruction, if taught in a secondary school field situation in a way which included specific applications to argumentative composition, would effect greater improvement in composition and logical sentence analysis than if the students received little or no instruction in composition in an English program. Eighteen English teachers, in grades 9 to 12, from seven schools systems, taught symbolic logic to some of their classes. Seventeen replications of the study and three replications of a control class were obtained. The study produced 1264 pupil essays for scoring and analysis. Results of the study include: (1) logic instruction had a statistically significant effect on scores on the sentence logic test; (2) logic instruction produced no noticeable improvement on pupils' essay writing; and (3) twelve teachers were generally positive in regard to their plans to teach logic again. Five appendixes are included: A. Logic Test; B. Directions to Students for Essay Writing; C. Guidelines for Evaluation of Essays; D. Subgroup Mean Scores on Sentence Discrimination Test; E. Subgroup Mean Scores for Essays. The results of the data analysis are given in 16 tables. (DB)