Amyotrophic lateral sclerosis (ALS) is a neurodegenerative motor neuron disorder of unknown etiology. Recently, in Alzheimer's disease (AD) apolipoprotein E (APOE) alleles have been shown to play an important role in disease phenotype. To determine whether APOE have a similar influence in other neurodegenerative disorders, we studied APOE genotypes in 130 sporadic ALS patients, compared with controls. We also analyzed APOE genotypes regarding ALS clinical criteria. The frequency of APOE genotypes was not different between ALS and controls. However, subjects with the APOE2/E3 genotype showed a significantly longer duration of the disease: 51 months vs. 28.5 for APOE3/E3 and 27.5 for APOE3/E4 (p = 0.001 and p = 0.02, respectively). There was a significantly higher proportion of bulbar ALS patients in the APOE3/E4 group (72% of the cases), whereas 90% of patients in the APOE2/E3 group showed limb onset (p = 0.01). In the bulbar group, patients with APOE4 showed earlier onset of the disease: 60 vs. 66 years (mean age, p = 0.05). These results are consistent with a protective role of APOE2 and a deleterious role of APOE4 in ALS as already found for AD. This parallel supports the idea of a general role of APOE in neuronal degeneration or regeneration rather than a specific role in ALS or AD etiopathogenesis.