The MAT-6 Writing Test (The Psychological Corporation, 1986) was administered to Oklahoma students in grades 7 and 10 in February 1989, in compliance with state law. The inception, implementation procedures, assessment instruments, and results of the Writing Assessment Component of the Oklahoma School Testing Program are described. District-level data are reported for the 1988-89 assessment, and state-level data are provided for the writing assessments conducted from 1987 through 1989. Guidelines are also provided for the analysis and interpretation of the test results. A combination of holistic and analytic scoring procedures supplies data to assess student strengths and to determine areas in which skill reinforcement is needed. The Holistic Score Percentile Ranks, used to give an overview of the general quality of composition skill demonstrated by each student, were 54 for grade 7 and 78 for grade 10. The analytic scores are used to evaluate four specific areas of writing skill--sentence formation, word usage, content development, and writing mechanics. The MAT-6 Writing Test scores indicate that Oklahoma students were able to construct acceptable informal essays within the 20-minute time limit imposed during the test administration. The continuation and expansion of the writing assessment program is planned, and future directions are discussed. Appendices provide additional information about the testing program; Appendices D through F contain 91 pages of test results. The "Manual for Interpreting: MAT-6 Writing Test" is Appendix G and the "Supplement to the Norms and Technical Booklet" forms Appendix H. (SLD)