In a series of 50 children with optic disk drusen the anomaly was found to be associated with unusual properties. A cilioretinal artery was more frequent in the series with drusen than in a control series of the same age. The emergence and course of the central retinal vessels were studied in the right-sided fundi of 46 of the children and in two control series (the fundi of the "better" eyes of 46 strabismic children and the fundi of one of the eyes of 10 children or young adults with papilledema). Analysis of the measurements indicated that early branching of the central vessels and vascular tortuosity are so frequently associated with optic disk drusen that they can be considered features of the anomaly. On the other hand, the fundal vascular features in papilledema seem to be distinguishable by the method used from those associated with optic disk drusen. When the peripapillary choroidal vascular pattern was studied by fluorescein angiography, choriocapillaris filling was delayed in about the half of the angiograms. The aberrant vascular features found on and around optic disks with drusen can be explained by an embryonic affection of the developing vascular system at the optic nerve head. In this respect the anomaly seems to resemble congenital disorders of mesodermal origin.