This study examines non-completion of Year 12 at school for a nationally representative sample of young people who were 15 years old and still attending school in 2003. The study explores relationships between non-completion and selected socio-demographic and school-related factors, and changes in rates of school non-completion from the early 1980s to 2005. There is a particular emphasis on how socio-demographic and school-related factors over that period have influenced early school leaving. This study also examines the use of an alternative measure of ‘school completion’, which incorporates participation in a vocational education and training program after leaving school.