Fifty-three patients (34 who had diffuse scleroderma, and 19 who had CREST syndrome [calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, and telangiectasias]) were studied by noninvasive procedures, including resting electrocardiogram (ECG), continuous 24-hour Holter ECG monitoring, M-mode echocardiography, and 2-dimensional echocardiography. Only 22 patients (42%) had abnormalities such as conduction defects, supraventricular or ventricular arrhythmias, or ST-T changes detected on resting ECG. In contrast, using Holter monitoring, the number of conduction abnormalities seen increased from 10 to 16 patients and transient ST-T changes increased from 2 to 18 patients. Forty-eight patients had ventricular arrhythmias, with multiform ventricular premature beats in 21 (40%), pairs of runs of ventricular tachycardia in 15 patients (28%), and 1 or more runs of ventricular tachycardia in 7 (13%). Echocardiography detected asymmetric septal hypertrophy in 10 patients, impaired ventricular function in 9 patients, congestive cardiomyopathy in 2, mitral prolapse in 4, and pericardial effusion in 3 patients. Multiform and/or repetitive ventricular premature beats occurred more frequently in patients with echocardiographic abnormalities, but were also present in patients who had normal findings on echocardiographic examination. Cardiac involvement was not correlated with clinical variants of scleroderma (CREST syndrome or diffuse scleroderma), nor with other signs and symptoms of the disease. Thus, cardiac involvement is found much more frequently than would be expected from clinical symptoms or from results of resting ECG alone; therefore, Holter monitoring and echocardiography should be included in the routine workup of patients who have scleroderma.