In 1984, the Connecticut General Assembly authorized the creation of mastery tests in mathematics and language arts (listening, reading, and writing skills) for grades 4, 6, and 8. Criterion-referenced tests were developed to assess the essential skills that should be mastered at the end of grades 3, 5, and 7 and to identify students in need of remediation. Connecticut educators identified the skills and determined their appropriateness for each grade. The Grade 4 Mastery Test results for 1990 are provided. The Grade 4 Mathematics Test assessed 25 objectives in conceptual understanding, computational skills, problem solving/applications, and measurement/geometry. The 104-item language arts test covers reading/listening and writing/locating information and examines nine objectives. In 1990, fourth-graders mastered an average of 21.2 of the 25 objectives, up slightly from the preceding year's figure of 20.6. In language arts, fourth-graders mastered an average 6.3 of the 9 objectives, as they did the preceding year. Writing scores and reading scores for grade 4 increased slightly. The scoring of the tests and equating to enable comparison with other years are discussed. Results for 1985 through 1990 are compared. Twelve charts summarize student achievement data. Thirteen appendices present test construction practices, specific objectives, the remedial standard setting process and committees, an overview of holistic scoring and marker papers for holistic scoring, the analytic rating guide and marker papers for analytic scoring, sample mastery test score reports, fall 1990 state by district reports in mathematics and language arts, the percentage of students meeting the statewide goal in each content area by district on the Connecticut Mastery Test, types of community classifications, education reference group descriptions, and student participation rates. (SLD)