Knowledge of the timing and course of neonatal intracranial hemorrhage is essential in determining the etiology of hemorrhage, since the key to preventing neurologic damage in newborns is to define preventable causes and to treat the complications of hemorrhage. In an intensive study of 49 neonates delivered less than or equal to 32 weeks gestation, the initial hemorrhage typically occurred in the first three days of life, with 36% occurring on day 1, 32% on day 2, and 18% on day 3. Most of the major hemorrhages (Grades III and IV) occurred on day 1, although ventricular enlargement occurred at a variable time after the initial insult. By the sixth day, 91% of all intracranial hemorrhage had occurred.