Scanning electron microscopy (SEM) was used to study vascular casts of 20 cadaver eyes according to our previously described technique. All eyes were taken from patients with long-standing diabetes mellitus type I. The SEM findings in the choroidal vessels included: increased tortuosity, dilation and narrowing, hypercellularity, vascular loop and microaneurysm formation, "drop-out" of choriocapillaries, and sinus-like structure formation between choroidal lobules. To our knowledge, these are the first SEM studies of the vascular casts performed on human cadaver eyes from diabetics.