Ultrasonic radiofrequency (RF) signals returned from the myocardium may display complex behavior, including deterministic chaos, and such chaos may be a useful marker of the tissue properties that are not obtainable with myocardial integrated backscatter. Thus, RF signals were obtained from the myocardium by the transthoracic approach in seven healthy subjects and eight patients with dilated cardiomyopathy (DCM). They were analyzed by a time-delay embedding technique to construct a continuous 3-D trajectory. The attractor formed a thick ring-like structure consisting of a relatively empty, roughly circular, core region in all healthy subjects. In DCM patients, the ring-like structure is thinned with a distinct empty circular core region. When the relation between embedding dimension and averaged correlation dimension was compared, the correlation dimension reached a plateau at the value of 3.5 in healthy subjects, and at the value of 2.6 in DCM patients. In conclusion, chaotic behavior is prevalent in the RF signals for the healthy myocardium, and a decrease in such chaos may be indicative of the damaged myocardium in DCM patients.