Peroral pneumocolon examination was performed on 40 patients for further radiographic evaluation of the terminal ileum after antegrade small bowel study. Patients were selected because of poor visualization of the terminal ileum on routine study (17 patients), clinically suspected Crohn disease but normal terminal ileum on routine study (ten), abnormal terminal ileum on routine study (seven), and previous ileocolic anastomosis (six). Use of the technique resulted in additional diagnostic information in 20 (50%) of the 40 patients. Its main value was in showing a previously poorly visualized terminal ileum to be normal (eight patients) and in confirming a normal terminal ileum in clinically suspected Crohn disease (six). In addition, it more precisely defined the proximal extent of recurrent ileal Crohn disease in two patients and detected otherwise unrecognized early ileal Crohn disease in one patient. The technique can be carried out immediately after any antegrade small bowel examination, and if reserved for the above indications, is a valuable adjunct to routine compression spot films of the terminal ileum or reflux study of the terminal ileum at barium enema.