Objective. To investigate the frequency of hypercalciuria and the relationship between hypercalciuria and hematuria in patients with juvenile rheumatoid arthritis (JRA). Methods. Twenty-eight children with JRA were studied, as well as 10 patients with acute arthritis unrelated to JRA and 14 healthy children as control groups. Cases with urinary calcium excretion (UCE) >4 mg/kg/day were considered hypercalciuric. Urinalysis was performed for detecting hematuria in all cases. Results. UCE was 4.19 ± 2.9 mg/kg/day in patients with JRA, 1.94 ± 1.57 mg/kg/day in children with acute arthritis, and 2.0 ± 1.45 mg/kg/day in healthy children. UCE was significantly higher in JRA compared with the other study groups. Of the 28 patients with JRA, 13 (46.4 %) had hypercalciuria and 6 (21.4 %) had hematuria. UCE was significantly higher in hematuric patients with JRA than in those with no hematuria (p<0.05). UCE in patients with JRA without hematuria was also higher than the UCE values detected in the disease and healthy control groups (p<0.05). Conclusion. Hypercalciuria is a frequent finding in patients with JRA [13/28 (46.4%)] and should be considered during the investigation of hematuria in patients with JRA.