OBJECTIVES: To evaluate body mass index (BMI) and its correlate plasma leptin levels that have been associated with psychiatric morbidity and suicidal behaviour, in relation to clinical features in psychiatric patients after a suicide attempt. METHODS: BMI and plasma leptin were assessed in 198 patients (66 males, age range of 21 to 80 years) who were admitted to the hospital after a suicide attempt, 98 with major depressive disorder, 28 with bipolar disorder, 30 with psychosis, and 42 with personality or adjustment disorder, compared to data of 134 healthy subjects, and evaluated in relation to gender, diagnosis, mode of attempt, and pharmacological treatment before attempt. The ratio leptin/BMI was used as a measure of adipocyte leptin secreting activity. RESULTS: Drugs taken for treatment before attempt, among them atypical neuroleptics, were not associated either to BMI or to plasma leptin. The positive correlation between BMI and leptin was significant in all groups. Compared to same gender controls, significant differences were found only for female patients, namely higher BMI for patients with psychosis and patients with bipolar disorder, while leptin/BMI ratio was higher only in females with bipolar disorder. CONCLUSION: BMI and plasma leptin in psychiatric suicide attempters are elevated in certain diagnostic groups in females, not related to previous pharmacologic treatment. The lack of a control group without a history of suicide attempts does not allow the attribution of enhanced leptin secreting activity found in female bipolar attempters specifically to suicidal behavior or to the disorder as a diagnostic entity.