Abstract: OBJECTIVE To study the plasma BDNF levels in schizophrenia patients with positive or negative symptoms before and after olanzapine treatment. METHODS Schizophrenia patients with positive symptoms, schizophrenia patients with negative symptoms and healthy controls were recruited based on the criteria of inclusion and exclusion. The two groups of patients received olanzapine treatment. Positive and negative syndrome scale (PANSS) questionnaire was used to estimate the response to olanzapine treatment. Plasma BDNF levels from the healthy controls and two groups of schizophrenia patients before and after olanzapine treatment were determined by ELISA method. RESULTS Significant negative correlations were obtained between PANSS scores and plasma BDNF levels both before and after olanzapine treatment in the patients with positive symptoms(P<0.01). In this group, plasma BDNF levels before olanzapine treatment were significantly lower than those of healthy controls. Furthermore, good or median response to olanzapine treatment had obviously increase in plasma BDNF levels when compared to those before treatment, while BDNF levels were not enhanced significantly in treatment-resistant patients. Neither significant change of plasma BDNF levels nor significant correlation between PANSS scores and plasma BDNF levels was observed in schizophrenia patients with the negative symptoms before and after olanzapine treatment. CONCLUSION Plasma BDNF could serve as the index of treatment response of olanzapine in schizophrenia patients with the positive symptoms.