Australia has one of the higher rates of suicide among young people. Although a role for doctors and teachers in the prevention of youth suicide has been suggested, no prior Australian study has assessed adequately the level of suicide knowledge held by these professionals. Knowledge about adolescent suicide was investigated using the Adolescent Suicide Behaviour Questionnaire, a 39-item instrument developed for the purpose. The stratified random sample comprised 404 general practitioners and 481 teachers from 56 secondary schools. General practitioners and teachers scored, on average, 71% and 59% of the questionnaire items correct, respectively. There was wide individual variability: The number of items correct ranged from 4 to 38 for general practitioners and 0 to 34 for teachers. Strengths and deficits in knowledge across the two professions are discussed in terms of the potential gatekeeping role of these professionals in suicide prevention.