Little is known about grammatical sophistication in the written language of school-age children. This study provides normative data on the occurrence of different complexity levels of major grammatical parameters in written compositions of nine-year-old children. These parameters include productivity of language, correctness of language usage, the frequency of occurrence of the T-unit (minimal terminable syntactic unit), extent of vocabulary diversity, and extent of expressed abstractness. Results also suggest dimensions of similarity and of difference between grammatical sophistication of oral and written language. Findings can contribute to the development of classroom instructional activities within a written language program. A list of references and a table of findings are included. (Author/JM)