In order to advance our understanding of the mechanisms through which women come to be underrepresented in mathematics and science, factors associated with the academic choices of students in three grade ll classes were studied. Information was gathered through questionnaires, interviews with students and with their mathematics teachers, classroom observations, and examination of academic files. Among the many variables examined, the only one that turned out to be correlated with both sex and academic choice was confidence in one's ability in mathematics: boys expressed more confidence than girls and students choosing a science program expressed more confidence than students making other choices. The results of this study are consistent with sex-related differences observed in causal attributions of success in mathematics (by students as well as by teachers), and in classroom interactions (girls having fewer public interactions with their teacher). It was also observed that girls, but not boys, were facing a conflict between career and family plans. (Author/JM)