Hypercalciuria is of continuing interest as a risk factor for kidney stones in children. We screened 592 healthy Turkish children (308 boys, 284 girls, aged 3 month-16 years) for hypercalciuria by measurement of urinary calcium/creatinine (UCa/Cr) ratio in the second-morning urine samples. Hypercalciuria was noted in 17 children (2.9%), 9 of them were boy and 8 of them were girl. Oral calcium-loading test could only be done in 7 children who were diagnosed as having hypercalciuria, and it revealed absorptive hypercalciuria in 2 cases and renal hypercalciuria in no cases. The frequency of a family history of urolithiasis in asymptomatic hypercalciuric children was 50%. Median UCa/Cr ratios and urinary magnesium/creatinine (UMg/Cr) ratios were 0.11 and 0.10 and the 97th percentiles were 0.32 and 0.23 respectively. The UCa/Cr ratio in second-morning urine samples was correlated with the UMg/Cr ratio (r = 0.44) and was independent of age and sex.