A chronic granulomatous syndrome of unknown origin. A small clinically distinct group of patients with widespread tissue granulomata are described. The principal presenting symptoms are malaise, fever, and weight loss, although a wide variety of complaints are documented. Pulmonary involvement is uncommon. The granulomata are noncaseating with a few multinucleate giant cells and some surrounding chronic inflammatory infiltrate. There is no evidence of an associated arteritis. The disease has a relapsing and remitting course and although it may require treatment with immunosuppressive drugs, particularly if the kidneys are involved, the prognosis is relatively good. We propose that this entity be called granulomatous syndrome of unknown origin. The characteristics that set this syndrome apart from the other granulomatous vasculitides are discussed. The current limited understanding of granuloma formation does not allow us to propose a definite etiology for this condition. It is emphasized that it is not helpful to encompass it within a label of sarcoidosis. First, it may only serve to confuse the doctor in assessing and treating this very particular group of patients. Secondly, it may hinder future attempts to understand the different pathogenetic mechanisms underlying the various conditions in which granulomata may arise. 