Treatment of most primary mediastinal tumors is based on positive histological diagnosis; we describe a variation of anterior mediastinoscopy under local anesthesia. After infiltration with local anesthetic, a transverse skin incision is made in the second, third, or fourth interspace. The endothoracic fascia is incised vertically adjacent to the periosteum and a mediastinoscope is inserted in the mediastinum. Between 1995 and 2001, we have employed this technique in 46 patients with anterior mediastinal tumors. Histological diagnosis was obtained in all patients. Pneumothorax (2 patients) was drained by a tube removed at the end of the procedures. No other complications occurred and all patients were discharged from hospital within 24 hours. Mediastinoscopy under local anesthesia proved safe and effective for diagnosing anterior mediastinal tumors.