We encountered a patient in whom remitting seronegative symmetrical synovitis with pitting edema (RS3PE) developed after treatment with UFT. A 64-year-old man who had cervical and lung metastases of unknown origin was treated with docetaxel hydrate, cisplatin, and 5-fluorouracil. Subsequently, the patient received UFT at a dose of 300 mg/day. Shortly after starting treatment with UFT, symmetrical pitting edema developed in the dorsum of the hands and feet. Since the results of immunological examination were consistently negative for rheumatoid factor, the patient was given a diagnosis of RS3PE. The symptoms of RS3PE markedly improved after the withdrawal of UFT and the start of steroid therapy. The findings suggested that UFT may be related to the development of RS3PE.