There has been an National Institutes of Health consensus meeting concerning the management of patients with "asymptomatic" primary hyperparathyroidism, yet there is no clear definition of this condition. The authors, therefore, documented the clinical manifestations and frequencies of these manifestations in unselected patients with primary hyperparathyroidism and determined whether these clinical manifestations resolved after parathyroidectomy. The authors studied 152 unselected consecutive patients with primary hyperparathyroidism and 132 control patients with nontoxic thyroid disorders who were treated by parathyroidectomy or thyroidectomy, respectively, between January 1986 and June 1991. All patients received a questionnaire during their initial office visits and the same questionnaire again after their operations. Patients were also questioned about their perception of the success of the operation. Eighty percent of the parathyroid patients and 70.5% of the thyroid patients completed the questionnaires, and the mean follow-up time was 20 months. Only 7 (4.6%) patients with primary hyperparathyroidism had no symptoms, and 26 (17.1%) had no associated conditions despite 74.3% of these patients having serum calcium levels less than 12 mg/dL. Symptoms including fatigue, exhaustion, weakness, polydipsia, polyuria, nocturia, joint pain, bone pain, constipation, depression, anorexia, nausea, heartburn, and associated conditions, including nephrolithiasis, and hematuria occurred more often in patients with primary hyperparathyroidism than in the thyroid control patients (p < 0.05). After parathyroidectomy, only eight (5.3%) patients failed to have any improvement in symptoms or associated conditions. Fifty-seven percent of the parathyroid patients versus 30% of the thyroid patients felt better overall after the operation, strength subjectively improved in 29% of parathyroid patients versus 13% in thyroid patients; thirty-seven percent of the parathyroid patients versus 13% of the thyroid patients claimed they were less depressed. When examined thoroughly, few patients with primary hyperparathyroidism were asymptomatic or without associated conditions, and most patients experienced subjective improvement after successful parathyroidectomy.