This report presents results of the National Assessment of Educational Progress (NAEP) 1994 trend assessments in science, mathematics, reading, and writing. To provide a numeric summary to students' performance on the assessments, the NAEP used a 0 to 500 scale for each subject area. Comparisons of average scale scores are provided across the years in which trend assessments have been administered and among subpopulations of students. Nationally representative samples totaling approximately 31,000 students were involved in the 1994 assessments. Descriptions of trend results are based on the results of statistical tests that consider the estimates of average performance in each year as well as the degree of uncertainty associated with the estimates. Each sequence of results was tested for linear and quadratic trends, and these tests were supported by tests that compared results for selected pairs of assessment years within each trend sequence. In science and mathematics, the early decline has been replaced by improved performance in recent years. The overall reading trend has been one of only minimal changes, while writing results have been mixed overall. A procedural appendix explains the methodology of the four assessments. (Contains 28 figures, 69 tables, and 12 appendix tables.) (SLD)