PURPOSE: To evaluate the sensitivity and specificity of scintigraphy with technetium 9m white blood cells (WBC) for detection of colonic inflammation in children with and children without inflammatory bowel disease (IBD). MATERIALS AND METHODS: In 215 patients, uptake of Tc-99m WBC in 3,440 bowel segments was graded. In 137 of the 215 patients, the Tc-99m WBC scans were interpreted blindly and findings compared with results at colonoscopy and endoscopic biopsy. Planar, single photon emission computed tomographic, and maximum-activity-projection images were reviewed together. In 78 children without recent endoscopic biopsy results, Tc-99m WBC scan findings were compared with laboratory values, the gastroenterologist's initial clinical assessment, and findings at long-term clinical follow-up. RESULTS: In 128 of 137 children with recent biopsies, findings at histologic examination and on Tc-99m WBC scans were correlated. There were seven false-negative and two false-positive studies. Sensitivity was 90%, specificity 97%, positive predictive value 97%, negative predictive value 93%, prevalence of disease 53%, and overall accuracy 93%. In 75 of 78 (96%) children without recent biopsies, Tc-99m WBC scan findings were consistent with the laboratory values, gastroenterologist's clinical assessment, and long-term clinical follow-up findings. CONCLUSION: Scintigraphy with Tc-99m WBC is a useful noninvasive diagnostic test to determine the extent and distribution of inflammation in children with IBD.