Five cases of culture-proven Acanthamoeba keratitis underwent cryotherapy to the host cornea as an adjunctive treatment to medical and surgical therapy. Four of the 5 cases had progression of disease while receiving medical therapy considered to be appropriate for Acanthamoeba keratitis. One case underwent cryotherapy to the entire cornea after the disease had recurred in two penetrating keratoplasties; the organisms were eliminated but the patient never recovered useful vision. Two cases underwent cryotherapy to the host cornea at the time of a second penetrating keratoplasty. The organism was eliminated in both cases. Two cases underwent cryotherapy to the host cornea at the time of primary corneal transplantation with elimination of the organism and recovery of excellent acuity. This study does not provide conclusive evidence that cryotherapy eliminated the organism, but suggests that it can be an adjunctive measure to medical and surgical therapy. The risks of the adverse effects of freezing of the cornea must be weighted against the possibility of recurrence after keratoplasty with spread of disease to the sclera or to the development of corneal melting and perforation. Prevention of Acanthamoeba keratitis is by far the best approach to this disease entity.