We investigated the early changes in the choroidal vasculature in rats following surgically induced renovascular hypertension. Renovascular hypertension was induced in a group of 12 male Wistar rats using a modified Goldblatt procedure. The rats were divided into four groups, each being sacrificed at weekly intervals, the first group being sacrificed 1 week following the procedure. Vascular casts were prepared of the choroidal circulation using acyl resin (mercox). These were then studied using the scanning electron microscope. No abnormality of the choroidal circulation was noted for the first 2 weeks. At 3 weeks, when a rise in the average mean arterial pressure was noted, nodular lesions were seen in the choroidal arteries and choriocapillaris. These lesions were present in far greater numbers by 4 weeks. It seems likely that the nodular lesions described are microaneurysms and may contribute to the pathogenesis of the clinically described Elschnig spot.