The 1990 NAEP transcript data were used to study the number of Carnegie units (CUs) earned by students in seven categories of mathematics courses plus a miscellaneous category. On average, students earned 3.11 CUs, slightly more than the minimum of 3 suggested in A Nation at Risk (National Commission on Excellence in Education, 1983). Fifty-four percent of the CUs were earned in the standard high school sequence (Algebra 1 and 2 and geometry), and 20% were earned in preformal courses (e.g., General Math 1 and 2). Overall, gender and ethnic differences in the total number of mathematics CUs were small, but ethnic differences relative to the type of math course represented by the course categories were large. Gender differences in mathematics course-taking are discussed in light of differences in college attendance patterns and achievement variability. Implications of ethnic differences for school and curriculum reform are discussed.