We have investigated the categorical prevalence of hyperprolactinemia and examined the relationship between prolactin levels and subjective endocrine-related adverse effects in schizophrenia patients treated with amisulpride during a 1-year period. A total of 111 patients with schizophrenia who were either started on or switched to amisulpride were assessed for prolactin levels and endocrine-related adverse effects using 6 items derived from the Liverpool University neuroleptic side-effect rating scale (LUNSERS) at baseline, 8 weeks, and 1 year. 10 were antipsychotic-naïve, 23 were antipsychotic free for 1 month, 54 discontinued their medication during 1 month prior to study, and 24 maintained their antipsychotics at baseline. At 1 year, hyperprolactinemia was found in 75.9% of men and 85.7% of women. Significant increases in mean prolactin levels at week 8 in both sexes were found; this was followed by a significant decrease over 1 year only in women. The proportions of both sexes with hyperprolactinemia increased from baseline to week 8 but remained unchanged at 1 year. Scores on the endocrine-related items of the LUNSERS improved significantly from baseline to week 8 in both sexes and then remained consistent during maintenance treatment. Prolactin levels were significantly higher in the group with baseline hyperprolactinemia than in the group without baseline hyperprolactinemia at all assessment points. Amisulpride commonly induces hyperprolactinemia. Although the percentage of patients with hyperprolactinemia remained unchanged during maintenance treatment, serum prolactin levels significantly decreased among women. Self-reported endocrine-related side effects were not associated with prolactin elevation during amisulpride treatment.