Abstract:Biopsy specimens endoscopically obtained from the stomach, duodenum, sigmoid colon and rectum of 58 patients with rheumotoid arthritis (RA) were examined for amyloid deposition by light microscopy. Six cases (10.3%) were diagnosed as being amyloidosis. In cases with more than moderate amyloid deposition, amyloid was most notable in the lamina propria mucosae. In cases with slight amyloid deposition, amyloid was seen in the blood vessel walls of the lamina muscularis mucosae and tela submucosa. On the whole, amyloid deposition was most marked in the duodenum. Endoscopically, whitish, irregular, partially nodular thickening of mucosa was characteristic in the sites with severe amyloid deposition. A fine granular appearance was observed in the sites with moderate amyloid deposition. No particular abnormal findings were noticed in the sites with slight amyloid deposition. Erosions, redness and a tendency for easy mucosal bleeding appeared frequently in the sites with more than moderate amyloid deposition. The endoscopic abnormal findings were most remarkable in the duodenum, and mildest in the recto‐sigmoid colon. It was suggested that these abnormal findings were correlated with the degree of amyloid deposition especially in the lamina propria mucosae. All the amyloidosis cases were in advanced anatomical stages of RA. The degree of anemia was more severe, and total protein, albumin and total cholesterol values were lower in the amyloidosis cases than in non‐amyloidosis cases. It is clear that when endoscopic examinations of RA patients are done to rule out amyloidosis, a biopsy should be taken from a depth including the submucosa even if the endoscopic finding is nor