Prophylactic treatment of retinal tears, holes, and degenerations has proved very effective in a convincing series of results. Ever since prophylactic treatment became available the number of patients treated prophylactically has been growing worldwide annually. While it will never be possible to prevent all retinal detachments, no significant fall in the rate of retinal detachment has been reported. Yet this is what we expect from prophylaxis. Most patients with manifest retinal detachment have not in fact received previous prophylactic treatment for various reasons. The ophthalmologist involved in prophylaxis is confronted with large numbers of patients. Preventive treatment has to be highly selective to be practicable and safe. Only lesions presenting a definite risk of retinal detachment should be treated. The criteria for treatment must be revised from time to time. Three types of failure should be noted: (a) Retinal detachment "because of" prophylaxis, (b) Retinal detachment "in spite of" prophylaxis, (c) Retinal detachment in cases in which prophylaxis was omitted because of a "false negative diagnosis". On the other hand overtreatment and misuse, i.e. prophylactic treatment of innocuous lesions, based on "false-positive diagnosis", apparently takes place without reducing the incidence of retinal detachment but resulting in expense and stress to the patient and in some cases even in complications of treatment. It seems unlikely that we have reached the final stage in the prevention of retinal detachment. Screening techniques, selection criteria, treatment, and follow-up should be improved. Until there are fewer detachments to operate upon, much remains to be done.