Fifteen years after panretinal photocoagulation in the Diabetic Retinopathy Study, 86 (57%) patients had died, 14 (9%) could not be located, and 51 (34%) of 151 patients were examined to determine the long-term treatment effects. Of the eyes randomized to photocoagulation only 1 (5%) of 19 argon-treated and 1 (3%) of 32 xenon-treated eyes had received additional laser treatment, but 8 argon-treated and 7 xenon-treated eyes had had cataract removal. Eleven (58%) of the initially argon-treated and 13 (41%) of the initially xenon-treated eyes had 20/40 or better acuity, and 18 (95%) of the initially argon-treated and 26 (82%) of the initially xenon-treated eyes had 20/200 or better acuity. Of the control eyes 17 (33%) had 20/40 or better, and 30 (58%) had 20/200 or better acuity. Argon and xenon panretinal photocoagulation for diabetic retinopathy provide good results for at least 15 years.