To determine the incidence and risk factors of nephrocalcinosis in preterm infants, we studied in a prospectively 64 preterm infants of birth weight :5 1500 g from February 2006 to November 2007. Data were collected on gestation, birth weight, gender and family history of renal calculi, respiratory support, and use of nephrotoxic drugs. The parameters of mineral metabolism were assessed in blood and spot urine samples at the end of 2 nd and 4 th weeks of age. Forty-nine babies completed the study, and nephrocalcinosis was observed in 13 (26.5%) babies and was bilateral in 7 (14.3%) infants. The mean age of diagnosis of nephrocalcinosis was 52.58 days (range 30-123 days). Gestational age, birth weight, and sex were not significantly associated with increased risk of nephrocalcinosis. The mean duration of ventilation was significantly less in babies with than without nephrocalcinosis (P= 0.020), and the mean levels of urine calcium and phosphate at 4 weeks of age, respectively (P= 0.013, P= 0.048). There were also significant differences in urine calcium/creatinine ratio (P= 0.001), mean plasma levels of calcium at 2 weeks of age (P= 0.047) and plasma levels of phosphate at 4 weeks of age (P= 0.016) between babies with and without nephrocalcinosis. Using logistic regression analysis, family history of renal stone (P= 0.002) and urine calcium/creatinine ratio (P= 0.011) were significant predictors of nephrocalcinosis. However, there were no significant differences in the length of stay in the intensive care unit, duration of total parenteral nutrition, and duration and cumulative doses of nephrotoxic drugs between these two groups. We conclude that the incidence of nephrocalcinosis was similar in our population to the previous studies. Family history of renal stone and urine calcium/ creatinine ratio are the major risk factors of nephrocalcinosis in very low birth weight neonates.