Iridectomy specimens from 16 patients with clinically quiet chronic uveitis were analyzed by immunoperoxidase staining and compared to control iridectomy specimens from 11 non-uveitic patients. Nine of 16 uveitis specimens and none of the control specimens demonstrated a lymphocytic infiltrate consisting of interleukin-2 receptor-negative T helper and suppressor cells (P less than .003). Class II antigens were detected in the iris stroma in all uveitis specimens and six of the controls (P less than .006). Despite a quiescent clinical state, patients with chronic uveitis have increased expression of class II antigens in uveal tissue and have significant uveal infiltration of T helper and suppressor cells. These findings in a variety of types of uveitis give additional support for the importance of delayed type hypersensitivity mechanisms in human uveitic disease.