Distinct factors have been identified as potential predictors of antidepressant treatment response. Although autonomic function changes have been described in depressive subjects, their value as predictors of antidepressant response has not been systematically evaluated. Eight un-medicated patients with major depressive order (MDD) have their skin conductance (SC) and heart rate variability (HRV) measured at basal condition and during four induced emotional states: happy, angry, sad and neutral. The high frequency (HF) and low frequency (LF) power parameters of HRV were assessed. Subsequently, patients were treated with fluoxetine 20 mg/day for 8 weeks. The antidepressant response was measured with the Beck Depression Inventory (BDI). The BDI percentage reduction correlated significantly with HRV responses during sad condition in LF power, and during happy condition with LF/HF ratio. The BDI percentage reduction also correlated significantly with HR responses in happy and in neutral conditions, and also with SC responses in neutral condition. These preliminary findings indicate that automatic responses to induced emotions may predict antidepressant response in MDD patients. Confirmatory studies are warranted.