ABSTRACT. Meconium ileus and pancreatic changes, asRESULTS described in cystic fibrosis, were found, at autopsy, in a series of six infants who received prolonged neonatal intensive care for prematurity. Cystic fibrosis had not been suspected clinically. These pathological findings are so frequent in sick premature infants, amounting to 12% of all neonatal autopsies conducted over a period of 2 yr in our unit, that we question their specificity for cystic fibrosis and suggest they may be a manifestation of disordered physiology in the severely ill neonate. The diagnosis of CF in the neonatal period in the absence of a sweat test result is based on the post mortem findings of meconium ileus and pancreatic changes (1). These pathological findings have been described chiefly in infants dying from the complications of meconium ileus. The specificity of these changes has not been seriously questioned although there are sporadic clinical reports of meconium ileus occumng in the absence of CF (2-9). In none of these case reports is there an adequate description of the pathology of the bowel or pancreas.A series of six premature infants is reported, born over a 2-yr period, in whom meconium ileus and/or pancreatic changes were found at postmortem. None of these infants had any other clinical features suggesting meconium ileus attributable to CF. In view of the frequency with which a previously unsuspected diagnosis of CF was made at postmortem over the 2-yr period and the similarity of the clinical course in these infants, the specificity of the pathological changes for establishing the diagnosis of CF in the neonate is questioned. This diagnostic dilemma has obvious implications for recurrence risk counselling.In addition, IRT estimations were camed out retrospectively on serum samples from these infants and the results are discussed.