To evaluate the clinical utility of the spatial velocity electrocardiography (SVECG)-QRS complex in the diagnosis of dilated cardiomyopathy (DCM), studies were carried out on a series of 120 subjects divided into 5 groups. The two peaks of the SVECG-QRS complex pi-Mag and p2-Mag) were significantly depressed in the DCM group, compared to all other groups, that is, 30 normal subjects (p < 0.05, p < 0.01), 26 patients with aortic regurgitation and mitral regurgitation (p < 0.01, p < 0.01), 18 patients with diffuse hypertrophy (p < 0.01, p < 0.01), and 19 patients with cardiac dysfunction and ischemic heart disease with ventricular dilatation (p < 0.01, p < 0.05). Decrease in SVECG-QRS wave height in DCM patients is considered specific for DCM. When 26 DCM patients were divided into a subgroup [ventricular tachycardia, VT(+)] of 11 patients with a history of monomorphic VT (5*6 consecutive ventricular complexes occurring at a rate of 100 beats/min) and a subgroup [VT(-)] of 15 other DCM patients, pi-Mag was significantly depressed in the VT(+) subgroup compared to the VT(-) subgroup (71.5 ± 27.0 versus 97.2 ±31.2 mV/s, p < 0.05), and p2-Mag tended to be lower in the VT(+) subgroup (93.3 ± 39.9 versus 100.3 ± 34.0 mV/s). Both pl-Mag and p2-Mag were markedly depressed in the DCM patients who were claimed by VT. These data suggest that: (1) decrease in SVECG-QRS wave height is a new ECG sign of DCM; (2) marked depression in SVECG-QRS wave may be an important sign in predicting progress in DCM.