The purpose of this study is to better characterise, on the basis of a large number of cases and follow-up evaluations, choroidal abnormalities recently observed with indocyanine green (ICG) angiography in central serous chorioretinopathy (CSC). Digital ICG videoangiography was performed in 145 patients with active or inactive, acute or chronic CSC. Forty-eight patients were re-examined in a follow-up period of 6-22 months (mean 10 months). Areas of choroidal leakage attributable to hyperpermeability of the choriocapillaris were found in 98.6% of patients in association with active or resolved pigment epithelial leaks and pigment epithelial detachments. Diffusion of ICG into the choroid was characterised by rapid centrifugal spreading of the dye with a wash-out pattern which was particularly evident in areas corresponding to pigment epithelial detachments. In patients with a long-standing disease, when choroidal hyperfluorescence faded, hypofluorescent spots became increasingly evident revealing pigment epithelial alterations not shown by fluorescein angiography. Areas of choroidal leakage remained unchanged in each patient during the follow-up period, even when subretinal exudation resolved either spontaneously or after photocoagulation. In 5 eyes we observed the appearance of leakage points on pre-existing areas of choroidal leakage. Zonal hyperpermeability of the choriocapillaris characterises all the evolutional stages of CSC and seems to be the primary alteration of this disease. When it corresponds to pigment epithelial detachments choriocapillaris hypermeability is probably associated with local hyperperfusion.