Using an enzyme-linked immunosorbent assay (ELISA) sera from 100 individuals, 20 with motor neuron disease (MND), 25 with peripheral neuropathy (PN), 15 with degenerative dementia and 40 controls, were examined in order to detect serum IgM and IgG anti-GM1 and anti-GD1a antibodies. Patients with MND showed statistically significant higher levels of IgM anti-GM1 antibody compared to the control group. Three patients with peripheral neuropathy had very high levels of anti-GM1 and anti-GD1a antibodies. Antibody levels in patients with degenerative dementia showed no difference compared to the controls. These results suggest that a further inquiry into the role of serum anti-GM1 and anti-GD1a activity in motor neuron disease and peripheral neuropathy is necessary.