Primary hyperparathyroidism (PHPT) is known to cause diverse subjective symptoms, in addition to those related to osteitis fibrosa cystica and kidney stones. The treatment of the disease ameliorates the subjective symptoms and improves the patients' quality of life. In this prospective study, patients undergoing surgery for incidentally detected, mild, asymptomatic PHPT were assessed to determine whether subjective neuropsychological symptoms are improved even in patients with "asymptomatic" PHPT. From October 1995 to March 2004, 25 patients who had one or more neuropsychological symptoms preoperatively and were followed up 1 year after parathyroidectomy were enrolled. The subjective symptoms were identified using questionnaires distributed to patients; eight questions were used to determine the presence or absence of psychoneurological symptoms. Compared to their preoperative status, patients responded that their general health perceptions 1 year after surgery were improved (13 cases, 52%), unchanged (11 cases, 44%), or aggravated (1 case, 4%). There were no statistically significant differences in the patients' responses before and after surgery with respect to individual neuropsychological symptoms, such as "tiring easily, "forgetfulness," "decreased concentration," "depression," "irritability," "uneasiness," and "sleeplessness." Therefore, subjective neuropsychological symptoms did not improve in otherwise asymptomatic PHPT patients following parathyroidectomy. However, patients' questionnaire responses may not reflect their actual status as accurately as laboratory examination results. Overall, 52% of patients were subjectively satisfied with surgery; this may result from patients' expectations of treatment.