The clinical course of 47 patients with posterior scleritis is reviewed. Though clinical presentation varied widely, 73% of the patients presented with a visual acuity of 6/18 or less. Because the posterior scleritis was not always associated with pain or with anterior scleritis, the diagnosis was often not considered when the patient was first seen. The most common findings in the fundus were disc swelling, retinal detachment, and macular oedema and the most useful investigation was B scan ultrasound. No common aetiology was found, although 60% had a systemic disorder which was accompanied by a vasculitis. Those who were diagnosed and treated with the minimum delay had the most satisfactory visual outcome. However, there appears to be a group of patients with no underlying systemic disease who fail to respond to intensive therapy, and lose vision. A new sub-group of West Indians with the disease is described. The histopathology of 7 cases confirmed the presence of scleral vasculitis of the vessels in and around the sclera in all the specimens. Other significant findings include inflammatory swelling and focal loss of pigment epithelium together with choroidal vascular closure. This could account for the fluorescein angiographic findings.