The authors' objectives of this research were: (1) to assess levels of selfreported antidepressant adherence and reasons for nonadherence and (2) to investigate determinants of nonadherence. A group of general hospital and community psychiatry practice mood disorder outpatients (n=80) took a self-report questionnaire that assessed beliefs about antidepressants, self-efficacy, and reasons for nonadherence. High levels of adherence were reported: 58 patients (73%) indicated they took their medication as directed more than 80% of the time. Practical issues (e.g., simply forgetting or a change in routine) were the most frequently identified reasons for nonadherence. Patients were more likely to report nonadherence if they experienced a sexual side effect, had lower self-efficacy, were female, and had not completed post-secondary education. Clinicians should be cognizant of this complexity and address not only issues related to medication efficacy and tolerability, but also social mediators and health beliefs when prescribing antidepressants.