The neurodevelopmental status of 171 very preterm infants whose brains had been scanned prospectively with ultrasound was assessed blind at four years using a wide range of tests, including tests of cognitive function. Highly significant correlations were found between the ultrasound appearance of the brain and outcome. The probability of a major neurodevelopmental impairment among the 137 children who had a normal ultrasound scan or uncomplicated periventricular haemorrhage at discharge from the unit was 7 per cent; and for any neurodevelopmental impairment (major plus minor) it was 22 per cent. The probabilities for major, or any, neurodevelopmental impairment among the 18 children who had ventricular dilatation were 33 and 50 per cent, respectively; and for the 16 with hydrocephalus and/or cerebral atrophy (loss of brain-tissue from any cause) the probabilities were 56 and 69 per cent. Impairments predicted from lesions detected by ultrasound were largely neurological. There was no evidence that cognitive impairments could be predicted among infants free of neurological impairments.