This paper analyzes data from High School and Beyond, a two-stage nationally representative study of goals, attitudes, experiences, and achievement patterns of high school sophomores and seniors in 1980. The present study provides an indication of levels and patterns of sex-differentiated attrition from high school mathematics courses by determining specific points at which students in general, girls in particular, leave college preparatory mathematics sequences. It identifies predictors of persistence in terms of course numbers and transition from course to course. The relationship between course-taking in mathematics and the Scholastic Aptitude Test (SAT-M) quantitative scores is examined with the aim of providing evidence on the extent to which gender differences in mathematics course enrollment "explain" gender-specific scores. The final sample (N=8321) had at least some experience in academic courses in mathematics, representing those for whom skill in mathematics is likely to be required for future success. The findings show greater attrition of females as compared to males in less advanced courses with the reverse at advanced levels. The grade in the students' last mathematics course had a negative relationship to persistence and was greater for females than males. Results showed a strong relationship between socioeconomic status and persistence in mathematics. Evidence reported indicated that mathematics course-taking had a strong positive influence on SAT-M scores. (JM)