A study was undertaken to determine aspects of gender-related differences in mathematics achievement among 10th graders (n=253). More specifically, the following aspects were assessed: (1) gender-related differences and similarities on specific process-, content-, and micro-component aspects; (2) stability of the patterns of differences and similarities over a 2-year period; (3) similarity across genders of cognitive representations of reading and mathematics; and (4) similarity across genders in size and pattern of predictors of performance on mathematical processes. Teachers of English and mathematics administered, respectively, the Reading Comprehension and Mathematics tests of the Canadian Tests of Basic Skills, Form 5, to 10th graders in a city high school in May, 1987 and 1988. Fifty-eight males and 66 females were tested in 1987, and 57 males and 72 females were tested in 1988. Items of each test were grouped into content by skill micro-components, and raw scores for each micro-component were determined. Content and process component raw scores for each test were computed. Factor analysis, regression analysis, multivariate analysis, and analysis of variance were conducted. Factor matrices for males and females were very similar. Significant differences were found in favor of males on all three process components, on all but two content components, and on five of the micro-components. Patterns of observed differences were similar for the two yearly test administrations. Six data tables are included. (TJH)