In this prospective study, 217 children sustaining blunt abdominal trauma were initially evaluated with ultrasonography (US) and those with any abnormal ultrasonographic findings were further evaluated with computed tomography. Results of ultrasonographic examination were normal in 157 children and showed abnormalities such as free intraperitoneal fluid (FIF), intra-abdominal organ injury, and intrapleural fluid in 60 children. Computed tomographic examination of the 42 children with organ injury, the seven children with minimal FIF of no definite source, and the three children with intrapleural fluid revealed findings consistent with ultrasonographic findings. Computed tomographic examination of the eight children with more than minimal FIF of no definite source detected by US showed the source as liver injury in one and spleen injuries in two patients. The source of FIF could not be identified with computed tomography in five patients. After clinic follow-up examination, one of these five patients was operated on for abdominal tenderness, fever, and air-fluid levels detected on plain abdominal radiographs, and duodenal perforation was encountered. Clinical courses of the patients with normal ultrasonographic findings were uneventful. We conclude that US, aside from being a screening tool, is alone sufficient in the evaluation of the majority of the children sustaining blunt abdominal trauma. Although this is a preliminary study with further work needed to be done, we propose that further evaluation with computed tomography should be performed on those children in whom more than minimal FIF of no definite source is detected with US.