Objective: The objective of this study was to identify factors that predict the presence of urolithiasis detected with unenhanced computed tomography (UCT) in children. Methods: A retrospective study of all subjects <21 years of age who presented to the emergency department at Akron Children's Hospital and underwent UCT of the abdomen between January 2002 and December 2005 was performed. Demographic, clinical, diagnostic, treatment, and disposition data were abstracted by using a standardized form. Univariate and logistic regression analyses of factors associated with urolithiasis were performed. Results: A total of 339 eligible patients were identified, with 110 cases of urolithiasis detected with UCT for 95 individual patients. The mean age of the study patients was 14.4 years; 72 patients (66%) were female. In 17 cases (15%) of urolithiasis, initial urinalysis results were negative for blood. Fifty-seven stones (51.8%) were ureteral, 26 (23.6%) were renal, and 4 (3.6%) were in the bladder. Among children who did not have a stone identified through UCT, 23 cases (10%) of potentially significant, alternative diagnoses were identified. A history of urolithiasis, a history of nausea and vomiting, the presence of flank pain on examination, and >2 red blood cells per high-power field in urine microscopy were positively associated with urolithiasis. A history of fever or dysuria and costovertebral angle tenderness on physical examination were inversely associated with urolithiasis on UCT scans. Conclusions: UCT plays an important role in the diagnostic evaluation of children with flank pain. Approximately 15% of children with urolithiasis do not have hematuria.