A large retrospective clinical study is reported confirming pathologic studies upon the effect of hyaline membrane disease on the occurrence of intraventricular hemorrhage in very low birth weight infants. Two hundred and twenty infants with birth weight less than or equal to 1 500 g and gestational age less than or equal 32 weeks were studied. Infants with hyaline membrane disease (112) had 56% incidence of intraventricular hemorrhage whereas of those without hyaline membrane disease (108) only 31% developed intraventricular hemorrhage (p less than 0.001). When controlled for gestational age, the more immature infants (less than or equal to 1 000 g) exhibited no difference in the occurrence of intraventricular hemorrhage whether hyaline membrane disease coexisted or not. In the 1 001-1 500 g group, the occurrence of hyaline membrane disease with intraventricular hemorrhage was significant (p less than 0.001). The association of lower Apgar scores and the influence of intermittent positive pressure ventilation in infants with intraventricular hemorrhage is discussed. Extreme immaturity negates all perinatal clinical expertise in determining neonatal outcome. Therefore, carrying pregnancies beyond 28 weeks gestation is mandatory. Beyond 28 weeks, pulmonary maturity and the influence of therapeutic modalities and maternal transport become increasingly important.