Neutropenia has been shown to be protective in animal models of traumatic and ischemic brain injury. However, the relationship between changes in early neonatal blood counts with intraventricular hemorrhage (IVH) and cystic periventricular leukomalacia (PVL) has not been described. Objective: describe changes in the blood counts in infants with and without IVH and PVL. Methods: case-control study of infants with birth weight <1500g in a level III NICU from 7/93-7/97. White blood cell counts (WBC), absolute neutrophils count (ANC), platelet counts, nucleated red blood cell counts (NRBC) from admission (within 1 hour) and on day of life 1-3 were compared between infants with IVH (grade I-IV, n=61), PVL (n=15), and a control group with normal cranial sonograms (n=228). Data were analyzed with repeated measures ANOVA with post hoc testing and covariates of gestational age, growth restriction, preeclampsia, prenatal steroids, sepsis, chorioamnionitis, and 5 minute Apgar score. Data are expressed as mean± SD. Results: Infants with IVH had a higher WBC on admission(12.7 ± 15.1 vs 10.6 ± 8.6 mm 3, p<.001), day 1 (18.4± 17 vs 14.1 ± 11.5 mm3, p<.001), day 2 (17.3 ± 17.4 vs 13.0 ± 11.8 mm 3, p<.001), and day 3 (16.6 ± 2.6 vs 11.8 ± 10.1 mm 3, p<.001) compared to the control group. Infants with IVH also had a statistically higher ANC on admission and on each day from 1-3 compared to control infants. Infants with IVH had lower NRBC on admission compared to control (37 ± 62 vs 61 ± 115 per 100 WBC, p=.01) but had higher NRBC on day 2 (58 ± 18 vs 37 ± 128, p=.03), and day 3 (66 ±152 vs 23 ± 80, p<.001) compared to controls. There was no statistically significant differences in platelet counts on admission and at any time from day 1-3 in the infants with IVH compared to controls. There was also no statistical differences in the WBC, ANC, NRBC or platelet count on admission or at any time from day 1-3 in the infants with PVL compared to controls. Conclusions: in our population of infants <1500g, in the first 72 hours of life, IVH is associated with an increase in WBC, ANC, and NRBC. However, PVL is not associated with any changes in blood counts. Further investigation is needed to determine whether these changes contribute to IVH or are associated factors.