The object of this investigation was to determine the frequency of intracerebral periventricular haemorrhage in neonates with very low birthweights in an unselected material from the County of North Jutland. During the years 1988-1989 a total of 86 infants with low birthweights were born in the county. Intracerebral periventricular haemorrhage was diagnosed by means of ultrasonic scanning of the cerebrum and/or postmortem examination. Seven infants had to be excluded as neither of these examinations had been performed. The material thus consisted of 79 infants with a median weight of 1,196 gram (range 565-1,500 g) and a median gestational age of 30 weeks (range 25-37 weeks). Periventricular haemorrhage was found in a total of 13 infants, corresponding to 16% and the haemorrhages were found mainly in infants with gestational ages less than or equal to 29 weeks (32%). Haemorrhages with involvement of the parenchyma and/or dilation of the ventricular system comprised more than half of the cases of haemorrhage (8 out 13). The frequency of periventricular haemorrhage fell with gestational ages less than or equal to 30 weeks and the haemorrhages were less extensive. The respiratory distress syndrome and asphyxia were found to important risk factors for the development of periventricular haemorrhage.