The treatment of anterior mediastinal tumours is often subordinated to histological diagnosis. Sometimes topographic, radiographic and clinical criteria are sufficient to indicate surgical therapy. From January 1988 to June 1992, 31 patients (40.7%) underwent immediate surgery, while 47 patients (59.3%) underwent fine needle aspiration and Trucut biopsy under ultrasonographic or computed tomographic guidance. Thirteen of these patients had also an anterior mediastinotomy according to McNeill-Chamberlain technique. In 36 patients it was possible to verify accuracy of diagnostic procedures comparing these specimens with surgical histological reports. Only 3 patients had minimal complications. No patients undergone anterior mediastinotomy had morbidity or mortality. Our reports show that transthoracic fine needle aspiration and Trucut biopsy have a diagnostic accuracy of 72% and 83% respectively in identifying malignant from benign lesions. These procedures are not adequate to detail diagnosis for tumours with pleomorphic pathologic characteristics (diagnostic accuracy of 39% and 75% respectively). This disagreement is due to false-positive results (one for fine needle aspiration and four for tru-cut biopsies), this discordance occurred in lymphomas and thymomas groups. Such correct diagnosis is very important either for frequency of these tumours either for different therapeutic approach: chemo-radiotherapy in lymphomas and surgery in thymomas.