To facilitate the understanding of the anatomical localization of pulmonary lesions and to optimize diagnostic evaluation, a template was designed which, on conventional chest X-rays, could be employed to discriminate between central and peripheral pulmonary lesions. The term 'central' implies that the lesion should be visible in the tracheobronchial tree through a fibre-optic bronchoscope, and the term 'peripheral' suggests that the lesion is not visible through a bronchoscope. In 20 patients examined by fibre-optic bronchoscopy, the bronchoscope was wedged into four pre-selected segmental bronchi in each lung. Using fluoroscopy, the tip of the bronchoscope was marked out on the skin with leadshot. On subsequent chest X-rays, with posterior-anterior and right lateral views, the distances and angles of the markings of the bronchi were mapped out in relation to the main carina. These data were used to design the template.