Because 80% of patients with primary hyperparathyroidism have a single adenoma and because most adenomas are now visualized by ultrasonography, we have attempted to remove these suspected single adenomas under local anesthesia with intra-operative monitoring of urinary cAMP (UcAMP) and 1-84 parathyroid hormone (PTH) serum levels. In the last 2 years, 45 patients (mean age 65 years) with primary hyperparathyroidism underwent surgery with local anesthesia when a single adenoma was strongly suspected by ultrasonography. Patients with equivocal or misleading ultrasonography, e.g., those with associated thyroid or multiglandular pathology and those who were non-cooperative, were excluded from this procedure. UcAMP and 1-84 PTH were determined prior to the incision, at the time of removal of the adenoma, and at regular intervals until 120 minutes after the operation. Results were available 45 min to 60 min after sampling for PTH and 60 min to 80 min for UcAMP. Forty-two adenomas were removed through a 2 cm to 3 cm skin incision in a mean time of 25 minutes, with no adverse effect, no morbidity, and minimal discomfort. The 42 patients were normocalcaemic on follow-up. The monitorings always predicted the success of the operation. In the 3 remaining patients, because the monitorings remained elevated at the end of the procedure, the patients underwent classical bilateral neck dissection under general anesthesia. This new approach can be safely accomplished with short operative time and hospital stay. The absence of general anesthesia is reassuring for the patients who are reluctant to undergo general anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)