We reviewed the pathophysiology of gout in this review article. Gout occurs as a response to monosodium urate crystal (MSU) that is present in joints, bones and soft tissue. Hyperuricemia in gout is mainly due to the decreased renal clearance of uric acid and is considered to be the cause of MSU formation. However, hyperuricemia alone does not explain the development of gout. Acute gout attack is due to the response to MSU, which is derived by innate immunity. Tophi are deposits of MSU and cell debris surrounded by granulomatous inflammation. (Korean J Med 2011;80:251-254)