Mutations in the Super Oxide Dismutase gene (SOD1) lead to a dominant, inherited form of ALS (Rosen et al., 1993), and are well-studied with the hope that by focusing on the most penetrant and significant genetic defects associated with ALS, we may come to understand broader aspects of ALS disease onset and progression that are relevant to other ALS-associated mutations. This evidence concerns the gene SOD1 and amyotrophic lateral sclerosis.