While the emphasis and content of school mathematics differ little between Japan and America, by the time students reach junior high school, performance as measured by international studies differs greatly. This report provides a profile of the attitudes toward, strategies used, and performance on mental computation of Japanese students in grades 2, 4, 6, and 8, in order to identify factors that may contribute to this difference. Students in two randomly selected classes in each of grades 2, 4, and 6, and six randomly selected classes in grade 8 were selected from three elementary and one junior high school in Tshuchiura, Japan. Data were collected using a preference survey of numerical computation methods used, an attitude survey, a mental computation test, and interviews of selected students in grades 4 and 8. The major findings were that: (1) Japanese students thought both mental computation and written computation were important; (2) teacher attitudes toward mental computation varied; (3) students across all grades preferred mental computations; (4) a wide range of performance on mental computation was found; (5) performance levels on items presented visually was significantly higher than those presented orally; (6) performance on common items increased as schooling increased; (7) the range of mental computation strategies was very narrow; and (8) few students in the interview were able to express alternative strategies for mentally computing an item. Six appendices contain copies of the instruments and the categorization of anticipated strategies. (MDH)