Fulfilling a legislative mandate in 1984, Connecticut established mastery tests in mathematics and language arts (listening, reading, and writing skills) for grades 4, 6, and 8. Criterion-referenced tests were considered most appropriate for assessing achievement and determining individual remediation needs. The Grade 8 Mastery Test results for 1990 are provided. The Grade 8 Mathematics Test assesses 36 specific objectives in conceptual understanding, computational skills, problem solving/applications, and measurement/geometry. The 111-item language arts test covers reading/listening and writing/study skills. Eighth-graders mastered an average of 25.7 of the 36 objectives in mathematics tested, up slightly from the previous year's figure of 25.3. Eighth-graders mastered an average of 8.4 of the 11 objectives tested in language arts, up slightly from the previous year's figure of 8.0. Their writing and reading scores were equivalent to those of the preceding year. Procedures for scoring and equating scores for meaningful comparisons are discussed. Test results for 1986 through 1990 are summarized. Fourteen charts present 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)