Background: The aim of this prospective study was to evaluate urinary glutathione S transferases p (GST-pi), beta-2-microglobulin (B2-MG), and N-acetyl-beta-D-glucosaminidase (NAG) levels as markers revealing the effect of respiratory distress syndrome (RDS) on renal function in preterm infants. Methods: The study was performed with 76 preterm infants whose gestational ages were between 28 and 32 weeks. Twenty-six preterm infants with RDS (cases) and 50 preterm infants without RDS (controls) enrolled in the study. Blood and urine samples were obtained on postnatal (PN) day 3 and 30. Urinary GSTp levels were measured by enzyme-linked immunosorbent assay (ELISA), and urinary B2-MG levels were determined by nephelometric method. Results: There was no significant difference in urinary B2-MG and GST-pi levels between RDS and non-RDS groups on PN day 3 (P > 0.05 for each). However, preterm infants with RDS had significantly higher urinary B2-MG and GSTp levels than the control group on PN day 30 (P = 0.0001 and P = 0.031, respectively). Urinary NAG levels were higher in RDS group than those of the controls on both PN day 3 and 30, but these findings were not statistically significant (P > 0.05, for each). Conclusion: Preterm infants with RDS had increased levels of both GST-p and B2-MG levels on PN day 30, suggesting subclinical tubular dysfunction, probably secondary to hypoxic stress. (C) 2014 Wiley Periodicals, Inc.