The Ontario Student Drug Use Survey is a survey completed by the Centre for Addiction and Mental and is the longest ongoing study of adolescent drug use in Canada. The study, which spans over two decades, is based on 14 surveys conducted every two years since 1977.  In the spring of 2005, 7,726 students in grades 7 to 12 from 42 school boards, 137 schools and 445 classes participated in the survey administered by the Institute for Social Research at York University. This report describes drug use in 2005 and changes since 1977.