Forty-eight preterm infants (mean birthweight 1.0 +/- 0.3 kg; mean gestational age 28 +/- 3 weeks) underwent serial echocardiograms and physical examinations in order to determine the correlation between color Doppler flow mapping (CDFM) results and physical findings of a patent ductus arteriosus (PDA), the predictive value of early CDFM as an indicator of subsequent requirement for treatment of a PDA, and to determine the direction and duration of ductal shunting and the rate of ductal closure and opening. CDFM analysis and cardiac physical examination of left-to-right ductal shunting were usually concordant in infants with a large PDA shunt, the most reliable physical finding being increased precordial activity. CDFM studies on day 2 or 3 of postnatal life had prognostic value with regard to subsequent need for closing the PDA. Additional findings included the absence of right-to-left PDA shunting in infants < 1 kg and < 28 weeks gestation and the absence of ductal reopening in infants in whom it had closed spontaneously. After complete PDA closure using indomethacin, subsequent ductal reopening is uncommon, except in infants < 25 weeks gestation and < 700 g bodyweight.