The placental circulations of 25 normal and five complicated pregnancies were studied by color Doppler ultrasonography. Flow velocity waveforms were obtained in all 30 pregnancies and could discriminate between fetal and maternal intraplacental blood flow. We believe that color Doppler ultrasonography will improve our understanding of the pathophysiology of various pregnancy disorders that alter the placental circulations and that color ultrasonography is useful for the prenatal differential diagnosis of intrauterine masses.