OBJECTIVE To clarify the indocyanine green angiographic features of idiopathic submacular choroidal neovascularization. METHODS We performed fluorescein and indocyanine green angiography in 16 eyes of 16 patients (nine men, seven women; mean age +/- SD, 35.6 +/- 6.9 years; range, 24 to 48 years) with idiopathic submacular choroidal neovascularization. During the mean follow-up of 11.4 +/- 7.9 months (range, 1 to 28 months), angiography was repeated (mean, 2.6 +/- 0.5 times; range, 2 to 3 times) in 12 eyes and performed only once in four eyes. RESULTS In the early phase of indocyanine green angiography, a network of choroidal neovascularization was observed in 11 of the 16 eyes with well-defined choroidal neovascularization seen by fluorescein angiography. Choroidal hyperfluorescent areas were noted in 10 of the 16 eyes in the late-phase angiography. Three of the 10 eyes showed focal dilatation of choroidal veins within the hyperfluorescent areas. Choroidal neovascular membrane was located within the hyperfluorescent areas in eight of the 10 eyes with choroidal hyperfluorescent areas. A dark rim surrounding choroidal neovascularization was observed in 13 of the 16 eyes at the initial examination. Indocyanine green angiography was repeated in nine of the 13 eyes and in the other three eyes without dark rim initially. During the follow-up period, the dark rim became prominent in eight of the nine eyes and developed in one eye without dark rim initially. Choroidal neovascular membrane regressed in these nine eyes. Choroidal neovascularization remained active or enlarged in three eyes in which the dark rim was stationary or invisible. CONCLUSIONS The dark rim surrounding the choroidal neovascularization in indocyanine green angiograms appeared to reflect regression of idiopathic choroidal neovascularization. Choroidal vascular abnormalities such as hyperfluorescent areas or focal venous dilatation seem to be the background lesion predisposing to the choroidal neovascularization.