Amyotrophic lateral sclerosis (ALS) is a neurodegenerative syndrome with familial and sporadic forms. We conducted a study including 60 sporadic and 19 familial ALS patients, 206 reference patients with other neurological disorders and 1265 neurologically healthy controls to assess the Alzheimer-associated apolipoprotein E (APOE) epsilon4 gene variant as a possible risk factor for ALS. While no major influence of APOE epsilon4 on disease risk was detected, a gene dose-dependent effect with lower age at onset of sporadic ALS in epsilon4 carriers was found (p=0.027). These data support APOE epsilon4 as a subordinate contributing factor in ALS.