A 64-year-old woman was diagnosed as having rheumatoid arthritis in 1999 at a nearby hospital. She had been treated with etodolac, actarit, mizoribine (MZ) and prednisolone. On May 25, 2001, she noticed fever and nausea and was treated with diclofenac sodium and clindamycin. On May 31, a nasal bleeding, tarry stool, hyperuricemia, renal dysfunction and thrombocytopenia developed and she was admitted to our hospital. Administration of drugs except prednisolone was stopped and hemodialysis was carried out on June 1. Fever and nausea improved during several days. Hyperuricemia and renal dysfunction disappeared on June 11. The platelet count became normal after platelet transfusion and she was discharged from our hospital on July 2. She was also diagnosed as having Sjogren's syndrome. In our case, a delay in MZ discharge by transient renal dysfunction might have caused a hyperuricemia, following an aggravation of renal dysfunction. So, care should be taken about latent renal dysfunction during the use of MZ. Moreover, it may be necessary to consider a discontinuation of MZ and administration of hemodialysis in the case of transient renal dysfunction.