Canadian Journal of Behavioural Science 2007, Vol 39, No. 1, 1-22 1 Development and psychometric properties of the Early Development Instrument (EDI): A measure of children’s school readiness Magdalena Janus David R. Offord Offord Centre for Child Studies, Department of Psychiatry and Behavioural Neurosciences, McMaster University, Hamilton Author Note The authors would like to acknowledge The Founder’s Network, Invest in Kids Foundation, and Human Resources Development Canada for their financial support. We would like to thank teachers and parents in Toronto and Calgary for volunteering their time, and Eric Duku for his invaluable statistical expertise. Correspondence concerning this article should be addressed to: Dr. Magdalena Janus, Offord Centre for Child Studies, McMaster University, 1200 Main St. W., Patterson Bldg. Rm. 215, Hamilton, Ontario, Canada, L8N 3Z5.