We describe here two patients with rheumatoid arthritis who developed nephrotic syndrome after administration of bucillamine, a novel antirheumatic drug developed in Japan. The nephrotic syndrome occurred after six months' and five months' treatment of bucillamine, respectively. The renal biopsy showed early phase of membranous glomerulonephritis (stage 1) in both patients. The first patient was a 64-year-old man who had received gold therapy for two years, and penicillamine therapy for eight months before bucillamine therapy. The nephrotic syndrome occurred after one year's cessation of the gold therapy and six months' cessation of the penicillamine therapy. The other patient, 57-year-old woman, had no history of gold or penicillamine therapy. Our experience suggests that membranous glomerulonephritis might occur in relation to bucillamine therapy.