Blood volume and clinical data are reported on 8 premature and 3 full-term infants who presented with symptoms apparently due to polycythemia or hypervolemia. These cases termed 'symptomatic neonatal plethora' were caused by large placental transfusions associated with delayed clamping of the umbilical cord. Tachypnea, mild cyanosis, plethoric skin color, and neurological depression persisted on average for 30 h after birth. Chest X-rays showed mild cardiomegaly, pulmonary congestion and edema, and pleural effusions. Although the course was in general benign, phlebotomy was considered to be indicated in three infants to treat progressive clinical deterioration. The symptomatology and blood volume on these infants were compared with infants in an ongoing study with controlled time of cord clamping. Neonatal plethora must be considered as one cause of 'transient tachypnea of the newborn'.