The authors present their experience with the evaluation and follow-up of 62 patients with primary cysts of the iris, discuss their clinical and pathological features, and propose a simple classification for these lesions. The results suggest that the great majority of primary iris cysts, particularly those which arise from the iris pigment epithelial layers, are stationary lesions which rarely progress or cause visual complications. This finding is contradictory to the belief of certain authorities who stress that many such lesions lead to severe complications, with blindness and loss of the eye. The natural course of primary epithelial cysts differs from that of secondary iris cysts which follow surgical or nonsurgical trauma. The latter lesions do frequently enlarge and lead to severe complications such as inflammation and glaucoma. The major clinical importance of primary iris cysts lies in their similarity to neoplasms of the iris and ciliary body. It is concluded that the great majority of them are ophthalmic curiosities which require no treatment.