To investigate whether Fuchs' heterochromic iridocyclitis may be an immune complex vasculitis, we used an immunofluorescence technique to detect immunoglobulins and complement in iris biopsy specimens from nine patients with Fuchs' heterochromic iridocyclitis, 12 patients with other types of uveitis, and nine patients with glaucoma but without uveitis. No specific immune deposits were observed in the irises of the patients with Fuchs' heterochromic iridocyclitis. Immunoglobulin G, IgA, IgM, and complement were detected in patients with Fuchs' heterochromic iridocyclitis and patients with uveitis, and these results differed significantly (P less than .05) from the group without uveitis. The immune deposits were found only in the iris vessel walls. No light-microscopic evidence of an inflammatory vascular process could be detected. Further studies are necessary to investigate whether the immune reactants originate from the circulation or result from local formation.