An investigation into the lipid metabolism of fibroblast cultures derived from subjects with Batten's Disease and Huntington's Disease as compared with control subjects will be continued. The metabolism of essential fatty acids: linoleic, and linolenic acids will be investigated both in terms of their uptake by cells, and their conversion to the higher polyenoic acids. Lipid metabolism by brain cell cultures will be studied at various stages of their in vitro life span.