PURPOSE: To determine which perinatal risk factors influence neurodevelopmental outcome, we try to investigate which perinatal risk factors are correlated with Baley mental or psychomotor developmental index using BSID-II test (Baley Scales of Infant Development, II) in long term follow up of very low birth weight who received neonatal intensive care. METHODS: This study was performed on 56 very low birth weight infants with corrected age 24 months who were admitted to the neonatal intensive care unit. We analyzed correlation between perinatal risk factors and neurodevelopmental outcome assessed by mental and psychomotor developmental index. RESULTS: Mean birth weight was 1317.8+/-168.5g : Small for gestational age was 11 cases and appropriate for gestational age was 45 cases : Mean mental developmental index was 93.8+/-10.3 and psychomotor developmental index was 99.9+/-13.2. Mean developmental scale did not show any significant difference between perinatal risk factors, such as sex, ventilator care and its duration, hospitalization days, birth weight, small for gestational age. Mental or psychomotor developmental score was significantly delayed in the subgroup with grade III intraventricular hemorrhages and periventricular cyst. On cranial ultrasonogram, sinificantly low mental, psychomotor developmental score was found on the subgroup with grade III intraventricular hemorrhages and periventricular cyst formation larger than 3mm size (P<0.01). CONCLUSIONS: These findings suggest that grade III intraventricular hemorrhage and periventricular cyst larger than 3mm size are associated with poor prognostic risk factors regarding to low neurodevelopmental index score.