A double-blind study (covering 40 months) of 40 eyes with a pterygium which had not previously been operated on, was carried out to study the effect of post-operative irradiation. Nineteen eyes were treated by the 'bare sclera' operation technique only and in 13 cases (68%) a recurrence occurred within 4 months. In 18 eyes from the group of patients treated with Sr 90 irradiation on the 1st, 7th and 14th postoperative day (maximum 3 X 1000 rad) no recurrences were seen. Patients with a recurrent pterygium and diplopia, symblepharon, visual disturbances (growth over the pupil or severe astigmatism) or many previous operations, were treated by lamellar keratoplasty (Dake, 1980). The recurrences without these complications were treated with success by the 'bare sclera' technique and postoperative irradiation. Complications did not occur in any of the series.