Ocular toxoplasmosis and Fuchs' heterochromic cyclitis are well-defined diseases that have completely different clinical courses. We studied 13 patients (seven men and six women, ranging in age from 18 to 73 years) who had Fuchs' heterochromic cyclitis and the focal necrotizing chorioretinal lesions characteristic of ocular toxoplasmosis. The reason for this association is still unknown, as is the pathogenesis of Fuchs' heterochromic cyclitis. None of the patients had ciliary injection or posterior synechiae, but 11 of the 13 (84.6%) had keratic precipitates, anterior chamber reaction, and cataracts. Six patients (38.4%) had iris transillumination, two (15.3%) had glaucoma, and four (30.7%) had lesions in the fellow eyes.