The aim of this study was to correlate endoscopic, radiological and pathological observations in 30 patients with Crohn's disease, with involvement of the stomach and/or duodenum. The incidence of gastroduodenal involvement in our patients with Crohn's disease is about 3%. 22 of the 30 patients had intrinsic lesions of the stomach and/or duodenum; in 8 patients the lesions seemed to be produced by involvement from contiguous diseased bowel. Radiological studies and endoscopy of the gastroduodenal region are complementary. Endoscopy allows better visualisation of mucosal defects. Other features, for example a diminished expansion and the presence of contiguity lesions, are better demonstrated by barium meal. The mucosal lesions found at endoscopy are heterogenous, but irregularly-shaped ulcers and erosions in a disrupted mucosal pattern are typical for gastroduodenal Crohn's disease. Pathological examination of endoscopic "forceps"-biopsies permitted a conclusive diagnosis based on the presence of granulomas, in 15/22 (68%) of the cases with intrinsic gastroduodenal disease. This observation indicates that simple forceps biopsy is a very useful diagnostic tool. Involvement of the first part of the duodenum in Crohn's disease was complicated by a biliary fistula in two patients.