OBJECTIVES: Many antipsychotics are associated with hyperprolactinemia and sexual dysfunction. This study investigated the prevalence of hyperprolactinemia and amenorrhea and explored the association between hyperprolactinemia and sexual dysfunction. METHODS: We analyzed 285 patients with schizophrenia or schizoaffective disorder who had been taking antipsychotics more than one year, examining their serum prolactin levels and administering the Arizona Sexual Experience Scale (ASEX) to evaluate for sexual dysfunction. We conducted an ANCOVA to evaluate the effect of hyperprolactinemia on ASEX score and amenorrhea. RESULTS: We found hyperprolactinemia in 52.3% of the patients, finding it to be more common in females (60.8%) than in males (49%). Patients taking risperidone had the highest prevalence of hyperprolactinemia (86.5%), and patients taking aripiprazole showed no hyperprolactinemia. Amenorrhea prevalence was 21.5%. Hyperprolactinemia did not significantly affect ASEX scores, but it significantly affected amenorrhea. CONCLUSION: Many patients taking antipsychotics still experience hyperprolactinemia in a real clinical setting. The prevalence of hyperprolactinemia varies among antipsychotics. Clinicians should consider the possibility of antipsychotic-induced hyperprolactinemia, with its potential adverse effects, when treating such patients.