A prospective study of the optimal time for postoperative beta irradiation of pterygia in 54 eyes of 54 patients suggested that immediate postoperative irradiation, given as a single dose of 2000 rad, was associated with a lower rate of recurrence than a similar dose given 4 days postoperatively. The authors suggest that patients with recurrent pterygia, selected to have postoperative beta radiation, receive the radiation as a single dose of 2000 rad at the end of the surgical procedure.