Transthoracic needle biopsy (TNB) has emerged as the semi-invasive technique of choice for the diagnosis of localized intrathoracic lesions. Using CT, fluoroscopic, or sonographic guidance, TNB is highly accurate and safe when combined with expert pathologic interpretation of the aspirated specimen. This article details the preprocedural evaluation of the patient referred for TNB and discusses the technical aspects of performing the biopsy and processing and interpreting the material obtained. The reported results and complications of TNB are reviewed and followed by a brief description of the cost effectiveness of the technique and a comparison with alternative semi-invasive diagnostic techniques including bronchoscopic and video-assisted thoracoscopic biopsy.