Sequential fluorescein angiography, using fluorescein-labeled dextran molecules of several different sizes, was carried out in monkeys with intraocular inflammation induced with interphotoreceptor retinoid-binding protein. The vascular leakage seen with the dextrans was compared with that seen with standard fluorescein sodium angiography. The angiograms demonstrated that different-sized leaks appear in the retinal vessels in adjacent areas during the course of the inflammation. Most retinal vessels leaked only fluorescein sodium and no dextran of any size, suggesting that it is the unbound fluorescein that leaks out of these vessels and not fluorescein bound to plasma albumin. It was not possible to tell by clinical examination which areas would leak the larger-molecular weight tracers. Ultrastructural studies of the veins leaking the dextrans revealed areas of abnormal endothelial tight junctions, whereas the tight junctions were normal in areas where leakage occurred with fluorescein alone.