The effect of sectoral, scatter laser photocoagulation on proliferative sickle retinopathy (PSR) was investigated by reviewing fluorescein angiograms of 88 sickle cell-haemoglobin C patients enrolled in a controlled, randomised trial. Follow-up was for a median period of 2.9 years. Complete infarction of all PSR in an eye occurred in 7 of 74 treated eyes and 2 of 60 control eyes. Treatment resulted in significantly greater regression (decrease in number or size of PSR lesions) in eyes of patients aged < 25 years at enrollment but not in eyes of patients > or = 25 years at enrollment. Infarction of individual PSR lesions was significantly more common in treated eyes. Treated PSR was significantly more likely to infarct if small (< 15 degrees circumferential involvement) and if flat rather than elevated. New PSR was significantly less likely to develop in treated eyes.