The Australian Early Development Instrument (AEDI) is an Australian adaptation of the Canadian Early Development Instrument. As part of ongoing evaluation since its development in 2003, this study compares the teacher completed checklist of the AEDI against results from the Longitudinal Study of Australian Children (LSAC), which is a longitudinal study involving parent, teacher, and interviewer assessments of infants and preschool children. Using a sub-sample of children from Queensland, Victoria, and Western Australia, the authors compared measures for social competence, language and cognitive development, emotional maturity, and health and wellbeing. The authors found the AEDI has sound construct and concurrent validity, and showed moderate to strong correlations with LSAC measures on many domains.