The rapid injection into the coronary circulation of solutions containing microbubbles produces an ultrasonic contrast effect in the myocardium. The time-intensity curves generated by sequential videodensitometric analysis of contrast intensity, which is corrected for myocardial background intensity, resembles the curves used in indicator dilution techniques. Studies done in vitro have demonstrated a direct relation between contrast intensity and amount of microbubbles. In animal studies, measurements derived from these curves correlated with changes in myocardial blood flow assessed by microspheres but with varying controversial results. Differences between investigators in technique of injection and size of microbubbles injected are among the list of factors that will alter the time-intensity curve and explain some of the differences in results between investigators. Several factors limit the application of myocardial contrast echocardiography (MCE) to the quantitation of myocardial blood flow. Nevertheless, the results from multiple investigations suggest that the technique is sensitive to changes in perfusion and may be applicable to the evaluation of regional coronary reserve and assessment of the results of revascularization procedures. Peak intensity and area under the time-intensity curve have provided consistent results between investigators; therefore, these measurements have been used to assess regional coronary reserve in experimental studies and patients with coronary artery disease. Although the results are encouraging, they cannot distinguish well between normal and mild impairments in coronary reserve and are subject to larger reproducibility errors.(ABSTRACT TRUNCATED AT 250 WORDS).