Clinical correlations of antiganglioside GM1 antibodies are important because high titers of these antibodies may have therapeutic significance. To further evaluate this significance, we reviewed our experience with 78 patients who had the following diagnoses: amyotrophic lateral sclerosis (ALS), ALS syndromes in patients with gammopathy or thyroid abnormalities, cervical spondylosis simulating ALS, motor neuropathies, and chronic inflammatory demyelinating polyneuropathies (CIDP). Antiganglioside antibody titers were measured "blind" by ELISA assay at the neuromuscular clinical laboratory, Johns Hopkins School of Medicine. We conclude that anti-GM1 antibodies are found in a wide variety of neuromuscular conditions. Patients with classical ALS had a mean anti-GM1 antibody titer significantly lower than patients with CIDP or motor neuropathy. Patients with ALS associated with gammopathy or thyroid disorders had higher anti-GM1 titers than seen in classical ALS. The highest mean titer occurred in patients with CIDP, a treatable neuropathy.