Background Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) can sample the enlarged mediastinal lymph nodes which are unreachable by conventional bronchoscopy.It is a relatively simple and safe method to see beyond the bronchial tree.We describe and discuss its initial application and our experience.Methods From July 2009 to December 2009, 52 patients with undiagnosed enlarged mediastinal lymph nodes were accessed with EBUS-TBNA in the People's Liberation Army General Hospital.Conventional bronchoscopy was performed before EBUS-TBNA, and patients with endobronchial lesions were excluded from this study.Smears fixed in 95% alcohol and histological specimens fixed in formalin were sent to Department of Pathology.Results EBUS-TBNA was diagnostic in 33 (63%) patients, with diagnosis of lung cancer in 23 patients (14 patients of small cell lung cancer, eight patients with adenocarcinoma, and one patient of squamous carcinoma).Four patients, who had negative EBUS-TBNA results, were later diagnosed with malignancy at thoracotomy.One patient with negative EBUS-TBNA results died of cancer cachexia.The sensitivity, specificity, and positive and negative predictive value of EBUS-TBNA for the diagnosis of neoplastic disease were 85%, 100%, 100%, and 50% respectively.Among the 16sarcoidosis patients, who were diagnosed by a combination of the clinical and radiological information as well as pathological results obtained by EBUS-TBNA, nine of them had granulomas and benign lymphoid cells detected by EBUS-TBNA.The sensitivity, specificity, and positive and negative predictive value of EBUS-TBNA for the diagnosis of sarcoidosis were 56%, 100%, 100%, and 13%, respectively.Five patients with no definite diagnosis from EBUS-TNBA examination are under close follow-up.Conclusions EBUS-TBNA can provide a safe and effective method to sample mediastinal leisions suspected of malignancy.It also adds pathological information needed to make the diagnosis of sarcoidosis.