Objective: A marked relationship is known between low birth weight and reduced nephron number. In this study, it was aimed to investigate the effects of low birth weight on renal function and blood pressure in healthy children and adolescents. Methods: This study was carried out on 33 children (7 to 18 years) who were born with a birth weight under 2500 g. The control group was composed of 30 children born at term with a birth weight appropriate for gestational age. Urine microalbumin, N-Acetyl-β-D Glucosaminidase, sodium levels and blood urea nitrogen, creatinine, and cystatin-C levels were investigated in patients and the control group. The sizes of kidneys in both groups were examined by ultrasonography. Blood pressure was monitored for 24 hours as ambulatory blood pressure. Results: The study group had higher levels of blood cystatin-C, urinary sodium, and N-Acetyl-βD-Glucosaminidase than the control group. Kidney volumes were smaller in the study group than in the controls. Conclusion: In our study, we observed that some glomerular and tubular functions were affected in children with low birth weight and in children born preterm. These effects were not observed in children with mature small for gestational age. Considering that nephron formation is completed at the 37th week, gestational age (prematurity) was thought to affect glomerular maturation more than intrauterine growth retardation. Our findings did not demonstrate hypertension in children born with low birth weight in childhood. We suggest that low birth weight children should be followed carefully for renal functions and blood pressure.