While contrast echocardiography has been shown to delineate intracardiac shunts, no information is available concerning the sensitivity of the method. This study establishes the relative sensitivity of the technique in detecting and localizing shunts by comparing the contrast echocardiograms with the simultaneously recorded cardiogreen dye curves in 26 children during cardiac catheterization. The echocardiograms substantiated isolated intracardiac shunting as small as 5%. There were no false-positive or false-negative echocardiograms in patients with or without shunt defects. This report demonstrates the contrast echocardiographic technique to be extremely sensitive in detecting intracardiac communications. It reviews the diagnostic patterns necessary for diagnosis and proposes the technique as a sensitive, safe, and accurate alternate method of study in the cardiac catheterization laboratory.