Hyperprolactinemia is a frequent consequence of treatment with typical antipsychotic agents and atypical antipsychotics such as risperidone. Recent studies have suggested that aripiprazole, a partial dopamine agonist, reduces the prolactin response to antipsychotics. Thus, we conducted this study to evaluate the dose effects of adjunctive treatment with aripiprazole on hyperprolactinemia in stable schizophrenic patients maintained with risperidone.

Inclusion Criteria:

1. aged 18-45 years of and fulfilled Diagnostic and Statistical Manual of Mental Disorders(DSM-IV )criteria (American Psychiatric Association, 1994) for schizophrenia;
2. having a stable psychiatric condition, defined as taking the same dosage of risperidone for at least 6 weeks;
3. being treated with risperidone monotherapy; and presence of hyperprolactinemia associated with risperidone.

Exclusion Criteria:

1. any other major psychiatric disorder;
2. significant concurrent medical illnesses, organic brain disorder, history of substance and alcohol abuse, and mental retardation