Mutations in the Cu/Zn superoxide dismutase gene (SOD-1) are reported in 20% of familial amyotrophic lateral sclerosis (ALS) cases, but no definite report of a mutation in a "truly" sporadic case of ALS has been proved. We present the first case of a novel SOD-1 mutation in a patient with genetically proven sporadic ALS. This mutation (H80A) is believed to alter zinc ligand binding, and its functional significance correlates well with the aggressive clinical course and postmortem findings observed in this patient.