OBJECTIVE--To investigate interrelations between ventricular long axis function, resting electrocardiogram, and myocardial perfusion imaging in a group of patients with syndrome X in order to define possible underlying mechanisms. DESIGN--Prospective echocardiographic, electrocardiographic, and myocardial perfusion imaging. SETTING--A tertiary referral centre for cardiac diseases with invasive and non-invasive facilities. PATIENTS--50 consecutive patients with syndrome X selected on the basis of a history of angina, ST segment depression on exercise, and normal coronary arteriograms and 21 controls of similar age. RESULTS--Long axis motion of one or both ventricles assessed by echocardiography was abnormal in 37 patients. The onset of systolic shortening was delayed by > 130 ms (upper limit of normal 95% confidence interval) in eight patients, and was associated with prolonged shortening during the isovolumic relaxation period in seven (p < 0.01) (systolic abnormalities). The onset of diastolic lengthening was delayed by > 80 ms in 20. Early diastolic peak lengthening rate was < 4.5 cm.s-1 in 13 patients, and the relative amplitude of lengthening during atrial systole was > 45% in 18. On the resting electrocardiogram septal q waves were absent in 12 patients. This was associated with long axis systolic disturbances in seven patients (p < 0.05). T waves were abnormal in 10 and associated with delayed onset of early diastolic lengthening in all (p < 0.001). Late diastolic long axis disturbances were not associated with any consistent electrocardiographic abnormality. Myocardial perfusion imaging was abnormal in six of 33 patients, four of whom had systolic abnormalities (p < 0.03). Imaging was normal in the rest, but in 13 of them long axis function was abnormal in the left side and in four it was abnormal on the right ventricle. Both electrocardiography and imaging were normal in 10 patients. No patient with an abnormal electrocardiogram or myocardial perfusion had normal long axis motion on echocardiography. CONCLUSION--The function of the left and right ventricular long axes was abnormal in about 70% of a sample of patients with syndrome X. Systolic disturbances were consistently associated with absent septal q wave and abnormal myocardial perfusion imaging, while early diastolic disturbances correlated with T wave abnormalities. These associations suggest that the three different investigations detect related objective abnormalities in one or more subgroups of patients with syndrome X.