Doppler ultrasound recordings of velocities of flow across the mitral and tricuspid valves and in the hepatic veins, and their variation with respiration, were recorded in seven patients with constrictive pericarditis and in six patients with restrictive cardiomyopathy. Deceleration of mitral and tricuspid flow was also evaluated during apnea. Color flow Doppler was performed in order to evaluate mitral and tricuspid regurgitation. Eight healthy adults served as controls. The patients with constrictive pericarditis showed higher peak diastolic velocities of mitral flow, as well as marked increase of velocity of flow at the onset of expiration and decrease at the onset of inspiration. Reciprocal respiratory variation of the velocities were also observed across the tricuspid valve. The patients with restrictive cardiomyopathy showed moderate or severe mitral and tricuspid regurgitation. They also showed shorter deceleration of flow across the mitral and tricuspid valves during apnea. The pattern of flow in the hepatic veins showed reversal during systole with accentuated reversion during inspiration. These results suggest that patient with constrictive pericarditis and restrictive cardiomyopathy can be differentiated by comparing Doppler echocardiographic data, along with changes induced by respiration.