Regression of Urrets-Zavalia's syndrome was obtained in one case after treatment administered according to a strict sequence following keratoplasty for keratoconus: sympatholytic drops (guanethidine 5%-Ismelin) every 4 hours for 24 hours, followed the next day, when mydriasis had been slightly reduced, by parasympathomimetic drops (pilocarpine 2%). Marked myosis was observed and treatment discontinued. This resulted in recurrence of the mydriasis, but this was successfully treated by repeating therapy. Pilocarpine drops were progressively diminished, followed by a slow reduction of guanethidine drops over 8 weeks, resulting in only slight residual anisocoria. This treatment is based on the physiopathological concept of sympathetic spasm with parasympathetic inhibition, and it is suggested that reduction of spasm should be obtained before administration of therapy to stimulate the sphincter. Pharmacological data on the compounds employed are discussed.