Ultrasonic tissue characterization has shown the potential to yield information about structural and functional properties of cardiovascular tissue. The development of real-time two-dimensional integrated backscatter imaging has made feasible clinical investigations of ultrasonic tissue characterization, including detection of stunned myocardium in patients with acute ischemia, recognition of remote infarction, detection of cardiac allograft rejection, and study of diffuse myocardial involvement with systemic diseases such as diabetes mellitus. Technical improvements and scientific advances in the understanding of the interaction between ultrasound and tissue may open an even wider range of clinical applications. Even in its present, relatively preliminary form, tissue characterization appears to have the potential for clinical application. Additional clinical experience will stimulate refinements and increases in the diagnostic power of this promising approach.