Optical light and electron microscopy were used in studies into two cases of infantile GM2-gangliosidosis. The results are reported in this paper. The correlation has been evident between histological and ultrastructural findings. Reliable delimitation between two different variants of infantile GM2-gangliosidosis was achieved through biochemical investigation of postmortally cultured skin fibroblasts. A classical form with isolated hexosaminidase-A defect (Tay-Sachs disease) was distinguished from a second variant with complete defect of both isoenzymes of hexosaminidase (Sandhoff's disease). Biochemical investigation of postmortally cultured fibroblasts today has become indispensable to enlargement of autopsy findings from other storage diseases, as well.