Sixty patients admitted to an acute treatment ward in a provincial psychiatric hospital were assessed for their competence to consent to psychiatric treatment. A semi-structured interview was used to determine whether they met none, some or all of the four necessary criteria for competence outlined in the Mental Health Act of Ontario. Only 21 of the 60 patients (37%) met all four criteria necessary for a patient to be considered competent to make their own decisions regarding psychiatric treatment. The study outlines the major difficulties in the assessment of competence to consent to psychiatric treatment. Our findings suggest that 74% of patients found incompetent using the current definition in the MHA (Ontario) would fail almost any reasonable test. The implications of these findings are discussed.