The evolution of ultrasound findings in 59 infants with transient periventricular densities is described and the neurodevelopmental outcome of 53 of these infants was compared with 92 of 107 infants with normal ultrasound scans, born during the same 24-month period. Four of the 53 infants with transient periventricular densities developed spastic diplegia and 24 developed transient dystonia, whereas only 8 of the 92 children with normal ultrasound scans demonstrated this finding (P less than 0.001). Persistence of the densities for more than 10 days and the presence of densities in the trigone were especially related with subsequent problems. Postmortem findings in two infants and MRI studies in six infants also suggested that transient periventricular densities represent the milder end of the spectrum of periventricular leukomalacia.