We determined the incidence of hypercalciuria (HC) and its association with nephrocalcinosis and nephrolithiasis in 18 consecutive patients with Beckwith-Weidemann syndrome (BWS). Random, nonfasting urine samples were obtained from each patient. All patients had abdominal ultrasonography, most on several occasions. Four patients (22%) had HC. Of these, 2 had nephrocalcinosis, one had hyperechoic kidneys, and one had normal renal imaging. Serum calcium was normal in all patients with HC. Because we found that an increased prevalence in the occurrence of HC and its complications in a group of children with BWS, any child with BWS should be evaluated for HC.