This study has assessed whether chest pain occurring during or after a step test could improve the accuracy of exercise testing in the diagnosis of coronary artery disease (CAD). One hundred and fifty-three consecutive men underwent the double Master two-step test prior to diagnostic coronary arteriography. On hundred and twenty-five had CAD, 28 insignificant disease (NCA). The post-exercise ECG showed at least 0-5 mm of ischaemic ST depression in 71 (57%) of the men with CAD and in five (18%) with NCA. Ischaemic ST depression of at least 2-0 mm occurred in 24 men, all of whom had CAD. Chest pain occurred during or after the test in 78 (62%) men with CAD and in nine (33%) with NCA. The accuracy of diagnosis of CAD could be improved by combining the occurrence of chest pain in the test with a positive post-exercise ECG. Either a 2 mm positive post-exercise ECG with or without test angina or 0-5 mm to 1-9 mm positive post-exercise ECG with test angina was found in 56 (45%) of men with CAD and one (4%) with NCA. Thus the concurrence of chest pain during or after a double Master two-step test, together with ischaemic ST segment depression after the test, strongly suggests the presence of CAD.