Pheochromocytoma is a rare tumour that synthesis extensive amounts of cathecholamines. It is usually called a "ten percent" tumour, as it is inherited in nearly 10% of cases, extra-adrenal in 10%, bilateral, multicentric and malignant in also nearly 10% of cases. Nowadays, surgery of pheochromocytoma is very successful as a result of well equipped laboratory techniques, radiological diagnosis and pharmacological drugs in preoperative therapy and control examinations during surgery. Although the operative technique and anaesthesia are delicate, operative risk is reduced to minimum, and definite recovery can be achieved in almost all benign diagnosed pheochromocytomas. Unrecognized pheochromocytomas remain the main problem, often ending with sudden death because of cerebrovascular complications or myocardial infarction, and are diagnosed during autopsy. The aim of the study is to underline the principal characteristics of pheochromocytomas and evaluate the facts that influence the diagnosis and outcome of the treatment. Medical records of the patients operated on for pheochromocytoma in our Institution are analysed. From 1981 to 2001, 102 patients underwent surgery for pheochromocytoma, 71 females and 31 males, average age 42 years (range 9 to 71). Laboratory confirmation was based on 24-hour urine cathecholamines, and in 12 patients only plasma cathecholamines were determined. In imaging studies, we used ultrasound (US), computerised tomography (CT) and nuclear magnetic resonance (NMR). If there was a suspicion of inherited or extra adrenal form of a tumour, we also used Metaiodbenzilguanidine scan marked with radioactive I131 (I131-MIBG). Diagnostic confirmation of tumours localisation was completely reliable. In 89 patients adrenal pheochromocytoma was found (12 bilateral, 2 with paraganglioma). In 13 patients, pheochromocytoma was extra-adrenal. Inheritated character was registered in 18 patients (MEN2 in 16, NF-1 in 2). Malignant pheohromocytoma was found in 11 patients, in 4 of 13 with extra-adrenal tumours, and in 7 of 89 with adrenal tumours. We prepared all patients with diagnosed pheochromocytoma for operation with phenoxybenzamine in daily doses of 20 to 90 mg, no matter whether they were normotensive or with hypertension. Two days before operation, we included propranolol in the therapy in doses of 20 mg twice or three times a day. Surgery was done in neuroleptic anaesthesia. We performed 100 primary operations and 9 reoperations (in 2 patients, the first operation was carried out in another institution), and extracted 123 tumours. In 2 patients, during reoperation we extracted the opposite adrenal tumour, in one recurrent benign tumour, and in the others, reoperation was done because of recurrent malignant pheochromocytoma. Hypertension was completely corrected in 79% of operated patients, reduced in 13%, and in 7% there was no effect on hypertension We observed the following operative complications: peritonitis due to a small bowel lesion (1), infection and wound dehiscence (1), pleural effusion (1), pneumothorax (1), gastrointestinal haemorrhage (1), haemathoma (1), temporary hemiparesis (1) and seroma of the wound (1). There was no operative mortality.