Aim: One has to measure urinary enzymes and proteins to determine renal dysfunction and tubular injury in earlier stage during the course of disease. The aim of this study was to investigate the role of urinary NGAL (neutrophil gelatinase-associated lipocalin), IL-18 (Interleukin 18), and KIM-1 (kidney injury molecule-1) levels in determining early renal injury in pediatric patients with hypercalciuria (HC) and/or nephrolithiasis (NL) and to compare the levels of these markers between the sick and healthy subjects. Material and Methods: Urinary NGAL, KIM-1, and IL-18 levels were measured in 40 pediatric patients diagnosed with NL, 23 patients with HC, and 20 healthy controls. Results: A significant difference was found between patient groups (NL and HC) and healthy children with respect to urinary NGAL/cr ratio (p < 0.001). There were no significant differences between patient and control groups with respect to urinary IL18/cr and KIM1/cr ratios. Conclusions: We found that urinary NGAL is a useful marker for determining renal tubular damage in NL and HC. To our knowledge, this is the first study to report significantly increased urinary NGAL levels in NL and HC.