Studies to date have produced preliminary evidence that the personality traits of neuroticism, socially prescribed perfectionism (SPP), and self-criticism are associated with suicidal ideation and/or suicidal behavior in adolescents. With few exceptions, however, the existing research has been conducted with the use of cross-sectional designs such as case-control studies or analyses of correlations among psychometric measures. The current study was undertaken to extend the existing literature on the relationship between personality dimensions and suicidality by conducting a longitudinal evaluation of adolescents hospitalized for suicidal ideation or attempts. The study sample consisted of 78 adolescents who were admitted to an adolescent psychiatric inpatient unit for suicide ideation or attempts. Subjects completed measures of self-criticism, interpersonal dependency, self-oriented perfectionism, and socially prescribed perfectionism, as well as the broad, higher order trait neuroticism. Depression symptoms, hopelessness, and suicidal ideation were assessed at the beginning (time 1) and end (time 2) of their inpatient treatment. Readmissions were determined by a review of medical records 1 year after hospital discharge. The study found that after controlling for baseline symptoms, neuroticism was associated with posttreatment depression and suicidal ideation. After controlling for time-1 symptoms and neuroticism in multiple regression analyses, self-criticism was associated with posttreatment hopelessness and depression. Logistic regression analysis was used to identify predictors of readmission. Baseline suicidal ideation and neuroticism were predictive of psychiatric readmission within 1 year of discharge. The study concluded that neuroticism and self-criticism are potentially useful predictors of outcome in suicidal adolescents and can be assessed quickly and reliably. Therapeutic interventions that target self-criticism (e.g., cognitive-behavioral therapy) may be useful in the treatment of suicidal adolescents. 5 tables and 40 references