The subjects chosen by students in the senior secondary years are widely considered to be important in shaping educational and occupational futures. Differences in patterns of subject choice which are associated with the background characteristics of students are often seen as involving issues of equity between social groups. Concern over equity in subject choice is expressed in relation to mathematics and science because studies in those areas are regarded as the basis for entry to many programs of professional education. This paper examines levels of participation in science and mathematics at Year 12 and whether participation in those areas of study is associated with differences in personal, social, and school characteristics. It explores the extent to which differences in patterns of participation arise from interests and aptitudes developed earlier than the senior secondary years. Finally it investigates the extent to which students who follow science and mathematics courses in Year 12 enter higher education. There are few studies of subject choice in Australia which are based on student level data. Two important examples are the SCOPE project in Victoria (Taylor, Alder, & Harvey-Beavis, 1989) and the study of course choices in the Australian Capital Territory by Cooksey (1990). In the SCOPE project students from Years 10, 11, and 12 in Victoria are surveyed each year about the subjects they study and other information. It examines student enrolments in ten subject areas which embrace the full range of subjects and relates those enrolments to a number of student and school characteristics. Cooksey examined course area clusters (group of subjects) and course patterns (combinations taken by students) in the ACT but without relating participation in those patterns to student characteristics. The present paper is based on a more recent national study which involved student level data: the ACER Study of Subject Choice (Ainley, Jones, and Navaratnam, 1990). That study was commissioned by the Commonwealth Department of Employment, Education, and Training, to provide information about subjects studied by students in the final two years of secondary school and to relate the patterns of subject choice to students’ social and educational backgrounds.