Takayasu arteritis (TA), a primary arteritis of unknown cause, commonly affects the aorta and its main branches. Most patients with TA have stenotic or occlusive changes; aneurysmal degeneration is relatively rare, and renal artery aneurysms are extremely rare. We observed a fusiform, 7-cm renal artery aneurysm in a 57-year-old man with TA who had been followed up for 17 years. The patient underwent nephrectomy and resection of the aneurysm. Histologic examinations of resected specimens of the lesion showed characteristics typical of TA.