Sonography, contrast radiography, and endoscopy of the small and large intestine were performed in 32 patients, who had already undergone one or more intestinal resections for Crohn disease, with the aim of detecting possible relapses. Eleven patients proved to have had relapses; sonography revealed nine cases, with two false negatives and no false positives. Sensitivity proved to be 82%, specificity 100%, and overall accuracy 93.7%. Sonography enables the operator to distinguish between inflammatory and neoplastic lesions by means of structural study of the thickened bowel wall, paying particular attention to integrity of its layers.