Our objective was to demonstrate that right ventricular (RV) infarction could be demonstrated by intracardiac ultrasonography in a canine model. RV infarction is a common and important clinical condition in patients with myocardial infarction. Traditional methods for diagnosing RV infarction have limitations. Intracardiac echocardiography, in which an ultrasonic transducer on the tip of a catheter is placed intravenously into the RV chamber, should allow detection of RV infarction. Nine closed-chest dogs were studied. The animals were instrumented with a 10 MHz ultrasound catheter placed into the right ventricle. The right coronary artery was occluded with a balloon angioplasty catheter for 20 minutes and subsequently embolized with elemental mercury. Intracardiac ultrasound images were obtained at baseline, during balloon occlusion, and during embolization. RV cross-sectional end-diastolic and end-systolic areas were calculated and fractional area changes were calculated; RV wall motion abnormalities were also evaluated. The interventricular septal thickening was also calculated. The 10 MHz intracardiac ultrasound catheter allowed visualization of much of the RV chamber and interventricular septum. The RV cross-sectional area increased with mercury embolization, which was also associated with regional wall motion abnormalities. RV end-systolic area was 1.6 cm2 and end-diastolic area 3.9 cm2 at baseline; these increased to 4.8 cm2 and 6.5 cm2 after embolization (p < 0.05). Interventricular septal thickening remained unchanged. The echocardiographic features of RV infarction, which include RV dilation and RV regional wall motion abnormalities, could be demonstrated in a canine infarct model with a 10 MHz intracardiac ultrasound catheter.