The Canadian dangerous offender (DO) statute requires the assistance of psychiatrists and psychologists in evaluating offenders’ potential danger and risk of future offenses, without substantive supporting empirical clinical research on the topic. The present study compared 62 men facing Canadian DO applications to 2,414 non-DO sexual and violent offenders (ACs) and 62 non-DO offenders matched on offense type (MCs). DOs differed significantly from ACs on 30 of 45 variables and from MCs only on 6. More DOs than MCs had an extensive criminal history, were psychopaths, and had more school truancy. Compared with ACs, DOs had less education and more school adjustment problems, more disturbed childhoods, and more often were diagnosed with sadism, psychopathy, and substance abuse problems. Total sexual and violent offense convictions provided the best but weak distinction of DOs from ACs. The "three strikes" law is noted and early intervention in DOs’ criminal careers is discussed.