Diabetic eye complications, and particularly diabetic retinopathy, are the major cause of blindness in the working age groups of industrialized countries. Laser photocoagulation has been proven to reduce blindness due to retinopathy by at least 60% but even more patients would benefit if treatment were delivered at an early enough stage. High-risk retinopathy, though, may not cause visual symptoms, and when the latter occur it is often too late to reverse them. Hence, a screening programme for diabetic retinopathy should aim at detecting patients at risk when they can still be effectively treated. This can be achieved by regularly checking the patients' eyes. The screening programme's target, as defined by the joint World Health Organization/International Diabetes Federation Saint Vincent Declaration Working Group, is to reduce diabetes-related blindness by one-third or more in the next 5 years. The number of individuals to be screened is high, 30,000 per million total population per year, but available data indicate that this is feasible and that the initial investments in professional and material resources are more than justified by the reduction of preventable blindness and of the financial burdens that go with it. Indeed, prevention of the major cause of blindness in the working age group should rate the same priority as other widely deployed programmes, such as those to screen for cancer, neonatal hypothyroidism, and phenylketonuria. The concerted action of government health departments, patients' and professional associations will be vital for the successful implementation of this programme.(ABSTRACT TRUNCATED AT 250 WORDS)