Suicide is known to vary according to season, with peaks in the spring and troughs in the winter. The presence of psychopathology is a significant predictor of suicidality, and it is possible that the seasonal variation of suicide completion may be related to seasonality in the manifestation of psychiatric disorders common to suicide completers. In the current study, we evaluated 115 French-Canadian male suicide completers from the Greater Montreal Area for DSM-IV psychiatric disorders using proxy-based diagnostic interviews. Subjects were assessed for seasonal differences in the prevalence of DSM-IV psychiatric diagnoses just before their deaths. Diagnoses of major depressive disorder (MDD) without comorbid cluster B personality disorders, and schizophrenia were differently distributed between seasons. Most (63.4%) subjects with MDD committed suicide in the spring/summer (P =.038). However, closer examination revealed that depressed suicides with comorbid cluster B personality disorders did not show seasonality, while 83.3% of depressed suicides without comorbid cluster B personality disorders committed suicide in the spring/summer (P =.019). 87.5% of those suicides with schizophrenia committed suicide in the fall/winter (P =.026), and the only suicide with schizophrenia who died in the spring/summer was also the only one without positive symptomology. Our study is limited to male suicide completers, and results should not be generalized to women. We conclude that seasonal variation in suicide manifests itself differently in patients with different psychopathology. These findings indicate that assessment of suicide risk may need to include consideration of possible seasonal effects, depending on psychopathology.