Granulomas were found in 16 biopsied specimens from eight patients with the acquired immune deficiency syndrome (AIDS), a disease characterized by a profound suppression of the T-cell arm of immunity. The pathogens were Mycobacterium avium-intracellulare (1), Mycobacterium tuberculosis (3), Histoplasma capsulatum (2), Candida albicans (1), and unidentified in one patient. The sites of granuloma formation included the lung in two, the pleura in one, the liver in three, the bone marrow in six, the skin in one, and the lymph node in three cases. The granulomas were epithelioid in nature, with aggregates of epithelioid histiocytes and macrophages. They were by and large small and loosely formed, with minimal or absent lymphocytic cuffing. Although it is a well-recognized concept that T-cell and macrophage interaction plays an important role in the granulomatous inflammatory response, granulomas have been produced in experimental animals independent of cell-mediated immune mechanisms. Granuloma formation in AIDS patients may well represent a clinical example of such a phenomenon.