Giant cell arteritis (GCA) is a well-known entity, creating aortic valve regurgitation secondary to dilatation of the aortic wall. No direct involvement of the aortic valve leaflets has yet been documented. A 75-year-old woman with a history of polymyalgia rheumatica and Horton disease was admitted to the authors' institution with acute cardiac failure, severe left ventricular systolic dysfunction and grade III aortic valve insufficiency. The aortic valve was excised and replaced in the usual manner with a pericardial tissue heart valve. Histopathological examination revealed a non-bacterial granulomatous inflammation with giant cells, strictly limited to the valve leaflets. The present case appeared to be the first with isolated involvement of the valve leaflets by GCA, creating acute aortic valve insufficiency.