The diagnosis of secondary amyloidosis due to rheumatoid arthritis (RA) was confirmed by positive tissue staining using Congo-red and antiserum to amyloid A protein. Biopsied specimens were obtained mainly from gastro-intestinal tracts; small salivary glands of the lips as well as abdominal adipose tissues were also studied in a small number. The results were as follows: 1. Gastro-intestinal fiberscopies and biopsies were performed on 789 RA patients for the purpose of routine screening and follow-up for amyloidosis. Seventy-seven cases (10.5%) turned out positive for amyloid. Among the biopsied specimens taken from three different sites, the proportion of amyloid-positivity was 68.9% for gastric antrum, 76.5% for duodenal cap and 88.6% for the second portion of the duodenum, suggesting the higher sensitivity and efficacy of duodenal biopsy in studying secondary amyloidosis in RA. 2. 124 patients of RA complicated with secondary amyloidosis were studied clinically with special reference to its clinical characteristics and prognosis. (1) The mean duration of RA at diagnosis of amyloidosis was 15.4 years and all patients but two were in stage III or IV (Steinbrocker). (2) Gastro-intestinal symptoms were present in 58.1% of the cases, abnormal renal signs in 58.9%, cardiac symptoms in 39.5%, respectively. All of these findings had a significant association with poorer prognosis in secondary amyloidosis due to RA. (3) The 4-year survival rate of all the cases was 57.8%, while the 3-year survival rate for the group without symptoms and signs about amyloidosis was 100%. (4) The causes of death in 36 cases were renal failure (14 cases), infection (13 cases), cerebral bleeding (2 cases), myocardial infarction (1 case), pulmonary infarction (1 case), suicide (1 case) and unknown (4 cases). Patients with intractable diarrhea were mostly susceptible to the ensuing fatal bacterial infection.