The serum of 63 patients suffering from various clinical types of endogenous uveitis with unknown etiology was investigated for the presence of circulating immune complexes (CIC). None of the patients was suffering from a systemic disease usually associated with CIC. Significantly elevated CIC levels were detected in 2 women with chronic cyclitis. One of them was also suffering from paresis of the facial nerve. The investigation reported here indicates that C1q-binding CIC are of no importance in the pathogenesis of endogenous uveitis. On the one hand one should consider the possibility of local IC formation, on the other hand one should be aware of the fact that IC does not always represent a pathogenic factor but that it may also occur as a secondary phenomenon after non-immunologic tissue destruction.