Hydrocolonic sonography is an easy and harmless technique for the evaluation of the colon wall. In our study, 106 patients were examined by means of hydrocolonic sonography and colonoscopy. The results were compared. Polyps larger than 7 mm were detected, whereas smaller polyps were often missed. Colon cancers were found in 5 patients, and it was possible to stage them. In moderately to severely active forms of inflammatory bowel disease this technique was able to make a differentiation between ulcerative colitis and Crohn's disease. In elderly and very young patients it may well be the primary screening method for evaluating the bowel.