Ultrasound brain scans were carried out serially during the first month of life on 219 newborn infants of 32 weeks' gestation or less. Periventricular haemorrhage (PVH) alone was observed in 36.1% and ischaemic lesions in 17.8%. By comparison with PVH, ischaemic lesions evolved later (median 7 days vs 2 days), and were associated with a significantly higher frequency of persistent ventricular enlargement and increased mortality. Birth asphyxia, antepartum haemorrhage, recurrent apnoea, and septicaemia--events which are known to promote systemic hypotension--were all strongly associated with ischaemic lesions but not with PVH alone.