The Longitudinal Surveys of Australian Youth (LSAY) program studies the progress of several groups of young Australians as they move from school into post-secondary education and work. This technical report is the codebook for Wave 4 of the 2003 (Y03) cohort. It describes the contents of the dataset and provides an explanation of all the variables in that dataset. This report, published by the Australian Council for Educational Research (ACER), is part of the Longitudinal Surveys of Australian Youth (LSAY) research program.