Background: Alcoholism and depression are often comorbid. Studies suggest that depressed subjects with alcoholism have more chronic impairment and suicidal behavior than individuals with either diagnosis alone. The reason for higher rate of suicide and suicide attempts in comorbid subjects is uncertain. We explored clinical characteristics that may be associated with this increased suicidality. Methods: In all, 219 depressed subjects (n=62 males and n=157 females) without a history of any alcohol or substance use disorder and 129 (n=49 males and n=80 females) depressed individuals with a prior history of alcohol use disorder participated in the study. Demographic and clinical parameters were assessed and recorded. Results: Depressed subjects with a history of alcoholism had higher lifetime aggression and impulsivity, and were more likely to report a history of childhood abuse, suicide attempts, and tobacco smoking. Depressed suicide ideators with a history of alcoholism had higher suicide ideation scores than depressed suicide ideators without a history of alcoholism. Subjects with a history of alcoholism were younger at the time of the first depressive episode and first hospitalization than those without a history of alcoholism. Logistic regression analysis indicated that alcoholism was significantly associated with smoking and aggression. Suicidal behavior and higher suicidal ideation in depressed subjects with a history of alcoholism might be attributed to higher aggression scores in this group. Conclusion: The greater frequency of suicidal behavior and severity of suicidal ideation in major depression with comorbid alcoholism appears related to associated aggressive traits. Alcoholism, aggression, smoking, and suicide may have a common biological causal substrate.