Objective. Cystinuria is an inherited transport disorder due to defects in intestinal and renal transport of cystine and dibasic amino acids. Early diagnosis is required for some general and specific treatments because cystinuric patients have an increased risk of recurrent urinary stone formation. The prevalence of cystinuria varies widely in different countries. The aim of this study is to determine the prevalence of cystinuria among schoolchildren in Eskisehir, a central Anatolian city in Turkey. Material and methods. The sodium cyanide-nitroprusside spot test was applied to the first morning urine samples from 8260 schoolchildren (4087 female, 4173 male, aged between 6 and 12 years). Urine and blood amino acids were determined with paper chromatography and special cystine-homocystine chromatography were performed if a child had a positive spot-test result. Urinary cystine levels of two children were measured quantitatively. Results. Spot-test results were positive in four students. Increased levels of cystine and dibasic amino acids in the urine were determined with paper chromatography and cystine spots were also detected with special cystine-homocystine chromatography for these four students. Urinary cystine levels were elevated in two children whose urine could be studied. The prevalence of cystinuria in this study was 1:2065. There was no history or symptoms related to urolithiasis in these students. Conclusion. The prevalence of cystinuria in this study is higher than many other countries. Patients in Turkey with urinary stones or with symptoms related to urolithiasis must also be investigated for cystinuria.