We evaluated the usefulness of transvenous intracardiac echocardiography (TVE) in visualizing the myocardial contrast effect in dogs in vivo. A 7-mm transesophageal echo probe (5 MHz, Aloka, Inc.) was introduced into the femoral vein and advanced into the right atria of 14 anesthetized dogs. The tip of the probe was positioned to allow visualization of the left ventricle in it's short-axis view. Albunex® was injected into the left coronary artery (n=14) or the left atrium (n=11) while contrast effect was continuously monitored by TVE. The results indicate that TVE can provide continuous, high-quality images of the heart. Moreover, the observed myocardial contrast effect had a high degree of reproducibility. Correlation between peak intensity produced by the first and second Albunex® injections was excellent in terms of both anteroseptal area (r=0.90, n=14) and posterior area (r=0.84, n=10). Injection of Albunex® into the left coronary artery during LAD or LCX ligation (n=5) produced extremely clear demarcation between perfused and non-perfused areas. The myocardial contrast effect was also observed when Albunex® was injected into the left atrium (100%-Albunex, 11/11, 100%). Peak intensities in the anterior region after the first and second left atrial injections (n=11) were closely correlated. Because of excessive contrast enhancement of the left ventricular cavity, however, detection of myocardial contrast in the posterior region was difficult in 4 of the dogs subjected to left coronary injection and in all of those subjected to left atrial injection. This experimental study would thus appear to indicate that TVE is a sensitive method of observing the myocardial contrast effect that produces highly reproducible results. TVE also appears to be especially useful for continuous monitoring of ventricular wall motion and myocardial perfusion status during myocardial ischemia. Future application of this technique to humans in vivo will be useful in the precise identification of perfused areas, and may enhance the clinical value of contrast echocardiography.