Two cases of GM1 type 1 gangliosidosis demonstrated microvascular abnormalities of the conjunctiva, as well as skin abnormalities in one case. This abnormality was studied by light and electron microscopy of a conjunctival biopsy; cytoplasmic vesicles were noted in the endothelial cells, producing a mechanical narrowing of the lumen. This storage material is similar to that seen in the fibroblasts of skin and of visceral organs in GM1 gangliosidosis, as well as to the material described in the systemic mucopolysaccharidoses. The material probably represents a keratan sulfate-like material. The conjunctiva provides a ready source for biopsy and diagnostic evaluation.