We investigate the efficacy of probiotics in reducing the incidence and severity of necrotizing enterocolitis (NEC) for very low birth weight (VLBW) infants.A prospective, masked, multi-center randomized control trial will be conducted level III neonatal center to evaluate the beneficial effects of probiotics for NEC among VLBW (<1500 g) infants. VLBW infants who start to feed enterally are eligible and are randomized into 2 groups after parental informed consents were obtained. Infants in the study group are fed with Infloran (Lactobacillus acidophilus and Bifidobacterium bifidus) with breast or formula milk twice daily for 6 weeks. Infants in the control group are fed with breast or formula milk alone. The clinicians caring for the infants are blinded to the group assignment. The primary outcome measurement is death or NEC (≧stage 2).