Nine patients with syndrome X were compared with 2 groups of patients known to have coronary artery disease (CAD) (8 patients who developed regional wall motion abnormalities [group ECHO+] and 6 patients who showed only ST depression at echo-pacing [group ECG+]) and with 6 healthy volunteer control subjects. Left ventricular function at rest was normal in all patients. End-diastolic and end-systolic volumes (ml/m²) and ejection fraction were calculated at baseline and at peak of echo-pacing using a Simpson’s biplane method. No regional wall motion abnormalities were observed during the echo-pacing in patients with syndrome X or in the volunteers. End-diastolic volume decreased in patients with syndrome X, in the volunteers (from 47 ± 11 to 30 ± 12 and from 72 ± 7 to 38 ± 6, respectively, p <0.01 for both), and in ECG+ patients (from 48 ± 10 to 33 ± 6, p <0.05), whereas it did not change in ECHO+ patients. End-systolic volume decreased in patients with syndrome X and in the volunteers (from 17 ± 5 to 11 ± 4 and from 28 ± 6 to 16 ± 4, respectively, p <0.01 for both), whereas it did not change or else slightly increased in patients with CAD (from 18 ± 10 to 16 ± 5 for ECG+ patients and from 19 ± 5 to 24 ± 9 for ECHO+ patients, p = NS for both), regardless of whether regional wall motion abnormalities appeared. Ejection fraction decreased in ECG+ and ECHO+ patients (from 64 ± 12 to 52 ± 11 and from 62 ± 9 to 44 ± 13, respectively, p <0.01 for both), whereas it did not change in patients with syndrome X and in the volunteers (from 64 ± 8 to 61 ± 8 and from 61 ± 7 to 58 ± 7, respectively, p = NS for both). During echo-pacing in syndrome X patients no regional wall motion was detected. Left ventricular volumes and ejection fraction showed the same patterns of variation in these patients as they did in the healthy control subjects, in contrast with those patients with CAD, whether or not regional wall motion abnormalities appeared in the latter.