Transgenic mouse models of human SOD1 mutations have opened up an area of intense investigation into the pathogenesis of familial and sporadic amyotrophic lateral sclerosis (ALS). However, the human phenotype of the G93A SOD1 mutation-the most commonly studied mutation in rodent models-has remained essentially unknown. This complicates the interpretation and transfer of results from animal models. Here clinical, electrophysiological and genealogical data are presented from a large German pedigree with a G93A mutation in the SOD1 gene. This pedigree shows a highly homogenous phenotype which closely resembles the typical phenotype of sporadic ALS, thus implicating comparable disease pathology of G93A SOD1 ALS and sporadic ALS.