Several cerebrospinal fluid (CSF) studies have provided support for a possible role for the dopaminergic system as a biological correlate of suicidal behavior. Indeed, low CSF levels of the dopamine metabolite homovanillic acid (HVA) have been described in depressed patients with a history of suicide attempts. In this study, we assessed the dopamine receptor sensitivity in relationship to suicidal behavior by measuring growth hormone (GH) response to apomorphine 0.5 mg subcutaneously (sc) in 15 DSM-III-R (APA 1987) major depressive inpatients with a history of suicide attempts, compared to age-matched and gender-matched major depressive inpatients without a history of suicide. Patients with a history of suicidal behavior exhibited a significantly lower GH response to apomorphine than patients who never attempted suicide (t = 3.60, df = 1.28, p = 0.0012). Therefore, these results suggest that a blunted GH response to apomorphine could represent a biological marker of suicidal behavior.