Fifteen patients suffering from serpiginous choroiditis were followed up for 1 to 10 years (mean 4.9 years). There were 7 women and 8 men with ages ranging from 20 to 65 years (mean 35 years). In 13 patients both eyes were involved. Ten of the 15 patients had both inactive scars and fresh lesions when first seen. The individual lesions resolved in a few weeks but, due to the gradual extension of the primary lesions centripetally in the shape of halos or pseudopods, signs of activity were observed for 1 to 9 months after the initial examination. After an interval of 3 months to 4 years, new recurrences were found in 8 patients; in some of them progression was noticed on serial fundus photographs only. Central vision was lost in 6 eyes, in 2 of them due to a subretinal neovascular membrane. Progression and recurrences could not be prevented by antituberculous medication or systemic corticosteroids. The cause of serpiginous choroiditis remains unknown but, on the basis of the fluorescein angiography, occlusion of the uveal vessels, possibly due to an immune vasculitis, is suggested. Immunological studies revealed no signs of diffuse vasculitis. Of the histocompatibility antigens, HLA-A2 was found in five and HLA-B7 in 4 of the 6 patients studied.