OBJECTIVE Ileoscopy has become a routine procedure for the diagnosis of Crohn's disease of the terminal ileum. The aim of this study was to compare the diagnostic accuracy of small bowel barium examination with that of ileoscopy. METHODS In a retrospective study the two methods were compared in 55 patients with Crohn's disease. First, routine radiology reports and second, reevaluation of the small bowel barium study by gastrointestinal radiologists with scoring of examination quality were compared with the results of ileoscopy. RESULTS Using routine radiology reports, 66% sensitivity and 82% specificity were reached for inflammatory changes of the terminal ileum by small bowel barium study. Sensitivity and specificity increased to 68% and 91% with double reading by experienced radiologists. Disagreement between endoscopic and radiologic results changed from 31% to 27% and were mainly because of false-negative barium studies. Sensitivity and specificity of barium studies were influenced by the quality of the examination with a sensitivity of 91% and specificity of 100% when the quality was good. CONCLUSIONS In patients in whom the terminal ileum is successfully intubated, ileoscopy is superior to barium examination in the evaluation of Crohn's disease of the terminal ileum. Results of the barium study were strongly influenced by the quality of the examination.