OBJECTIVE--To assess the value of a chest radiograph in the performance of diagnostic cardiac catheterisation in adults. PATIENTS AND METHODS--340 consecutive diagnostic cardiac catheter procedures in adults at one institution. It is normal practice for primary operators to report the results of catheterisation using a graphical user interface database system. Data entry screens were modified to present a study questionnaire to assess the use made of the chest radiograph in the performance of the catheter procedure. SETTING--Tertiary referral cardiac centre. RESULTS--The chest radiograph was judged of value in only 12/340 procedures (4%). The radiograph influenced catheter selection in six procedures, the volume of injected radiographic contrast medium in five, and showed an abnormality important to the planning or conduct of the procedure in six procedures. A dual benefit was reported in five procedures. Utility of the radiograph was related to the pre-catheter diagnosis. It proved of value in only 2/283 (0.7%) procedures with a working diagnosis of ischaemic heart disease, influencing only catheter selection. Its utility was greater in congenital heart disease, contributing in 3/4 (75%) procedures, dilated cardiomyopathy in 2/6 (33%) procedures, and valvar heart disease in 4/35 (11.5%) procedures. CONCLUSIONS--In the performance of diagnostic cardiac catheterisation in adults access to a recent chest radiograph contributes little to the conduct of investigations performed for suspected ischaemic heart disease, but may be of greater value in congenital disease, valve abnormalities, and dilated cardiomyopathy.