The aim of the study was intraoperative assessment of surgical treatment used for primary hyperparathyroidism (PH) basing on immediate histopathological findings and of parathormone (PTH) concentrations in blood serum, the latter being determined before and after removal of the affected parathyroid glands.Material and methods. The study group consisted of 110 patients: 85 women and 25 men aged 16-72 years (mean 49.3), treated surgically for PH or its recurrence. Each patient was operated together with bilateral neck exploration. The identified parathyroid glands were assessed. The operation was considered successful if the cause of PH could be confirmed by intraoperative histopathological examination, and PTH level was found lower than 50% of its preoperative value. Negative results of intraoperative tests were considered an indication for wider exploration of the neck or another full imaging diagnostics in order to decide about reoperation.Results. Parathyroid adenoma was detected in 85 (77.3%) patients, proliferation of the gland in 18 (16.4%) and parathyroid cancer in 7 (6.3%). Basing on intraoperative microscopic and immunochemical examinations, the surgical treatment was found successful in 107 (97.3%) patients. PTH concentration was found normal in 94 patients, and significantly lower in 13. The operation was assessed as unsuccessful in 3 (2.7%) patients (2x recurrence of parathyroid cancer, 1x proliferation of parathyroid glands). A non-significant PTH drop was noted in 1 patient, and PTH increase in 2. One patient died because of disseminated tumor disease, and 2 patients received another imaging diagnostics and reoperation with good result.Conclusions. 1. Positive result of intraoperative histopathological examination together with a significant drop in parathormone concentration in peripheral blood serum are essential for successful surgical treatment of PH. 2. Negative results of microscopic and immunochemical examinations are an indication for wider neck exploration. If further procedure is still unsuccessful, a more profound imaging diagnostics is necessary followed by reoperation.