Background: Avoiding hyperoxia with oxygen saturation monitoring is important in the follow-up of very low birth weight (VLBW) infants. Role of oxygen-derived free radicals in the pathogenesis of necrotizing enterocolitis (NEC) has been well defined. However, a great majority of the evidence supporting the role of hyperoxia in NEC development are data from experimental studies and there are very few clinical studies. In this study, the association between NEC and average oxygen saturation (SpO(2)) levels in VLBW infants was researched. Methods: Average SpO(2) values of VLBW infants in the last 24 h were recorded prospectively with pulse oximeter. Average SpO(2) records were continued at least for 10 days starting from the first day after birth. In the follow-up, the average SpO(2) values of the patients who developed NEC and those who did not were compared. Results: A total of 127 VLBW infants were followed up. Thirteen patients developed NEC (Bell's classification >= stage II). No differences were found between the average SpO(2) levels (94.9 and 94.8%) of the patients who developed NEC and those who did not. It was found that average SpO(2) value higher than 93 or 95 was not a risk for NEC development (P = 0.693 and P = 0.771). Conclusions: In this study, no association was found between average SpO(2) values recorded in the first weeks of VLBW infants and NEC.