In this large multicenter cohort we aimed at: (i) examining the potential associations between C9orf72 repeat expansion and phenotype, site of onset, family history, therapy, and others comorbidities; (ii) exploring if ALS patients carrying C9orf72 repeat expansion differed from patients without genetic mutation in the survival profile, both in the whole sample and stratified by sex. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.