Questionnaires concerning the self-concept and evaluations of maths and French, as well as an intelligence test, were administered to secondary school students more than six months before they had to decide whether or not to take maths courses during the following school year. At the same time their school grades for maths and French were recorded. Students' decisions were related to self-concept, evaluations of maths and French, and aptitude measures, by means of discriminant analyses. Results indicated that sex, in combination with students' (positive) evaluations of mathematics, their achievements in mathematics and their intellectual abilities, as well as a focus on French and self-concept of French abilities, could adequately predict their choice of mathematics courses. No interaction effects were found between sex and the other predictor variables. These results suggest that stimulating more girls to choose mathematics during their secondary school years should focus upon achievement, self-concept and evaluations of mathematics in comparison with other options.