Mutations in the ALS2 gene cause juvenile-onset autosomal recessive amyotrophic lateral sclerosis (ALS) and hereditary spastic paraplegia.To assess the role of ALS2 among more common forms of ALS.DNA from 95 unrelated familial, 95 unrelated sporadic, and 11 early-onset ALS patients was screened for mutations in ALS2 by denaturing high-performance liquid chromatography and direct sequencing of polymerase chain reaction-amplified fragments. Each variant identified was also analyzed among control subjects. All 34 exons of ALS2 plus the 5' and 3' untranslated region were screened.We detected 23 novel sequence variants; however, none is disease-associated.Mutations of ALS2 are not a common cause of ALS.