The frequently seen side effect of hyperprolactinemia thought to be the 'price' paid for the antipsychotic treatment of schizophrenia. Various reports have linked the use of risperidone, an atypical antipsychotic drug, with the significant rise of prolactin levels. Thus, we set to assess possible difference between prolactin levels among schizophrenia subtypes in 45 male patients treated with stable doses (2-6 mg/day) of risperidone as antipsychotic monotherapy. All patients showed increased prolactin levels beyond the normal range, with a significant difference between the paranoid and all other groups (P<0.0001). Specifically, the paranoid patients' prolactin levels were higher than those of the schizoaffective and the disorganized ones. These results suggest that the blockade of higher dopamine activity in the paranoid schizophrenia corresponds to the prolactin increase, more than in the schizoaffective and disorganized subtypes. These findings are opposite of what was observed in the previous study of unmedicated patients.