Recurrent herpes simplex infection, usually benign and self-limited, can present as a chronic destructive process. Three such cases are presented in detail, and a fourth probable case, but without cultural documentation, is briefly described. These have in common, with seven previously reported cases, some form of immunologic impairment. Particular reference is made to the striking incidence of chronic herpes simplex in renal transplant patients undergoing immunosuppression and to the association of the infection with steroid therapy. Topical treatment with idoxuridine was apparently beneficial in two of the four patients.