A 65-year-old female was first treated under a diagnosis of rheumatoid arthritis at the age of 62 years. Just after subcutaneous rheumatoid nodules appeared, she suddenly complained of shortness of breath and vomiting. The diagnosis was overt congestive heart failure with complete atrioventricular block and severe mitral regurgitation. She was treated with temporary pacing, and a permanent pacemaker was implanted 1 month later. She suffered recurrence of congestive heart failure and died 8 months later. Autopsy revealed a giant rheumatoid nodule located on the mitral valve and extending to the atrioventricular node. Presumedly this solitary giant nodule had induced complete atrioventricular block and severe mitral regurgitation.