Current Year 12 students form the largest single group of Australian university admissions, comprising approximately half of all admissions at Australian universities. For those Year 12 students who continue to tertiary study at Australian universities, the courses studied in Year 12 play an important role in preparing them for that further education. Information regarding Year 12 course participation is therefore of serious interest to Australian universities. Unfortunately, reliable, detailed and consistent data in this area are not readily available at the national level. This paper addresses this lack of information by compiling data on Year 12 course completions from all Australian States and Territories into a single, national level data source. This data source allows an examination of Year 12 completions over the time period 2005 to 2010. It found that mathematics and science completions experienced only very minor growth from 2005 to 2010. Given the growth in applications and offers of university courses requiring a solid background in these areas, an amplified policy focus on increasing Year 12 participation in Mathematics and Science would likely be beneficial. University admissions practices have a role to play. Universities could investigate how to modify the details of their entry requirements and procedures to influence participation and curriculum at the upper secondary level in a more systematic way. This could include more widespread use of bonus entry points, prerequisites, or matriculation-like arrangements to better align students' preparation at school with the demands of tertiary study. Universities could adopt practices that were consistent with their distinctive institutional missions. (Contains 5 figures, 5 tables, and 6 footnotes.)