Selective catheterization of small vascular branches is easily accomplished since the development especially constructed catheters with minute tips, optimal torque control, and tip deflection by external manipulation (5). We have called this technic “guided angiography.” Exploration of the bronchial arteries by this method has been prompted by recognition of the part these small arteries play in diseases of the bronchial tree and mediastinal organs and in abnormalities of the pulmonary arterial circulation. The procedure and preliminary findings in guided catheterization of the bronchial arteries were reported earlier (6). Our experience with a larger group of cases has enhanced our knowledge and technic, and it is the intent of this paper to expand on these technical considerations and mention some of the pitfalls encountered in the procedure and its interpretation. Technical Consderations Despite the variability in number and site of origin (Fig. 1), selective catheterization of bronchial arteries is easily accomplished, especially with the catheter-deflector assembly previously mentioned. Preliminary aortography has been suggested by some authors (3) in order to map the number and sites of origin of the bronchial arteries, but we have found this unnecessary in the great majority of cases. The orifices of the bronchial arteries are sought usually at or slightly above the level of the left main-stem bronchus between the upper border of T5 and the lower border of T6. According to Lie-bow (2), 82.8 per cent of bronchial arteries originate in this area; 70.1 per cent according to Cauldwell (1). To search for the right bronchial artery, the tip should be initially oriented posteriorly and slightly to the patient's right with the patient in the supine position. The left bronchial artery orifices are more variable and should be searched for initially with the tip of the catheter posteriorly and to the patient's left and by rotating the catheter clock-wise toward the anterior aortic wall. The catheter should be moved slowly in and out, and rotated at the same time, until a “catching sensation”and or visual impression of “being hooked” is noticed. The injection for filming 2 is made by hand or with an automatic injector set for “stuttering” at low pressure. High pressure caused displacement of the catheter tip due to the jet phenomenon which in turn is a result of a rapid injection through an end-hole catheter. In the catheterized bronchial artery, free blood flow should be maintained. Stasis may indicate wedging of the catheter. With our minute tip catheter, obstruction of the flow in the bronchial artery is uncommon. Preceding and following the injection of contrast material, we flush the artery with heparinized saline solution with procaine. We routinely film with a 9-in. image intensifier, a 16 mm cine camera, and a film speed of 30 frames per second. Optical magnification of the image tube output is accomplished by the use of a 35–50 mm lens.