Seventeen patients with central retinal vein occlusion aged 40 or under were reviewed. Ocular involvement was characteristically unilateral, with moderate degrees of retinal haemorrhage, little retinal ischaemia, and a tendency to optic disc swelling. Visual prognosis was good. Follow-up showed that most patients have good general health and no involvement of the fellow eye. There was little evidence to support an inflammatory aetiology or underlying vascular disease in most of the patients. An alternative explanation for the development of CRVO in young patients might be a congenital anomaly of the central retinal vein.