The ability to predict which suicidal patient is at high risk for a serious attempt is an important clinical problem. On the basis of our clinical research, we hypothesized that self-disclosure may be an important personality variable differentiating suicide attempters and completers. We assessed 80 patients with depressive disorder, divided into four groups of 20 each: suicidal ideation only, nonserious suicide attempts, severe suicide attempts, and no suicidal behavior. Comparisons were also made with 20 healthy controls. All subjects completed Jourad's Self-Disclosure Questionnaire (JSDQ), as well as scales measuring depression/anxiety and hopelessness. The lack of willingness for self-disclosure significantly differentiated the serious attempters from the suicide ideators and mild attempters. The relationship of self-disclosure and more lethal suicide attempts did not appear to be mediated by depression, anxiety, or hopelessness. This preliminary study indicates that self-disclosure may be a promising field for assessment, therapy, and prevention in suicidal patients. Further studies are needed to investigate related variables, wider patients groups, and the use of different instruments.