The prevalence and clinical importance of false tendons were studied in 488 consecutive patients referred for echocardiography. Two hundred and eighty three (58%) patients had acquired heart disease, 91 (19%) had congenital heart disease, and 114 (23%) had normal hearts. Sixty six patients with normal hearts had innocent systolic murmurs and one had recurrent ventricular tachycardia. The overall prevalence of false tendons was 25% compared with 1.6% in a retrospective analysis of 763 cross sectional echocardiograms. When patients with innocent murmurs were excluded from statistical analysis, there was no significant difference in the prevalence of these tendons between children and adults, boys and girls, men and women, or between patients with acquired or congenital heart disease and normal patients. The prevalence of false tendons in patients with dilated left ventricles (57%), however, resembled that seen in necropsy studies. The prevalence of false tendons in patients with an innocent systolic murmur was 76% in children and 40% in adults, with an overall prevalence of 52%. False tendons are a common echocardiographic finding of no clinical importance except for their possible role in the genesis of innocent murmurs and ventricular arrhythmias. The echocardiographic detection of false tendons increases considerably when these structures are specifically sought and in conditions that result in left ventricular chamber dilatation.