To evaluate the acoustic tissue characteristics of the human coronary artery, the ultrasonic and the propagation velocity were measured using acoustic microscopy. An ultrasonic tissue characterization system with a scanning acoustic microscope (HSAM-500S) operating at 450 MHz was used. Coronary artery specimens were obtained by autopsy from 52 patients and were classified into three groups: normal, early stages of sclerosis, and advanced stages of sclerosis. Both the ultrasonic attenuation and the propagation velocity were significantly smaller in the early stage and larger in the advanced stage than normal. It was therefore concluded that coronary artery intima in the early stage showed an initial softening as compared with normal tissue, and was followed by increasing hardening in the advanced stage as a result of progressing fibrosis and calcification.<<ETX>>