ABSTRACT. This study aims to explore the relation between changes in myelin basic protein (MBP) and S100 protein (S100B) serum levels and prognosis in premature infants with periventricular leukomalacia (PVL). In our hospital, 78 premature infants with PVL and 43 normal premature infants were studied from July 1, 2007 to December 31, 2008. MBP and S100B serum levels were detected at 1, 3, 7, and 14 days after birth by using enzyme-linked immunosorbent assay. All infants were followed four times (once every 3 months) after discharge from hospital. Their intelligence quotient and physical development index were tested by using Gesell developmental scales. The MBP serum levels were significantly higher in premature infants with PVL at any time point than in normal premature infants. S100B serum levels gradually increased at 1, 3, and 7 days; peaked on the 7th day; and then gradually decreased to the normal level on the 14th day. The intelligence quatient and physical development index of infants with increased S100B and MBP levels on the 7th day were lower than those of infants who had normal S100B and MBP levels and those of normal premature infants. A negative relation exists between S100B and MBP 4339 MBP and S100B in premature infants ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (2): 4338-4343 (2015) serum levels and prognosis in PVL infants. An increase of MBP and S100B levels lasting >7 days could cause poor prognosis.