We report the case of a 54-year-old woman who presented on May 28, 2001 with sarcoidosis overlapping with rheumatoid arthritis. She had experienced morning stiffness 2 years previously and was diagnosed as having rheumatoid arthritis. She had been treated with bucillamine and loxoprofen for 3 months. In October 2000, she developed proteinurea. The patient discontinued treatment with bucillamine and loxoprofen. Proteinurea persisted, and the patient's renal function declined. On admission, subcutaneous nodules were palpable in the patient's legs. The patient's serum creatinine and calcium levels were 2.49 mg/dl and 11.6 mg/dl, respectively. Intact-PTH was suppressed, and PTHrP was not elevated. Despite the presence of hypercalcemia, the patient's serum 1 alpha 25(OH)2D3 was not suppressed. Serum ACE and lysozyme levels were elevated beyond the normal ranges. A renal biopsy was performed, and non-caseous epithelioid granuloma was found in the renal interstitium. Based on the histological findings, the patient was diagnosed as having sarcoidosis. Following treatment with prednisolone, the patient's serum calcium levels returned to normal and her renal function improved.