OBJECTIVE An autoimmune basis has been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). This hypothesis is supported by the presence of antibodies that interact with motoneuron antigens in serum of these patients. Against autoimmunity are the discrepances in the frequency of the antibodies appearance and also failure of immunosuppression. The aim of our study was to evaluate the titer of antibodies against GM1-gangliosides, AGM1-gangliosides and anti-sulfatides in paired serum and cerebrospinal fluid samples in the ALS patients. METHODS Serum of 103 and CSF of 79 patients with ALS was examined. The "disease controls" consisted of 22 cases of other motor neuron diseases and 50 healthy, age-matched normals. CSF was drawn at the same time from 79 ALS patients, 6 cases of the "disease controls" and 50 normals. To study the titer of antibodies against GM1-gangliosides, AGM1-gangliosides and sulfatides the ELISA technique has been applied. RESULTS An increased titer against GM1-gangliosides, AGM1-gangliosides and sulfatides in ALS appeared in serum in 18%, 32%, and 11%, resp., in the "disease controls" the increased antibodies titer appeared in single cases. In CSF the appropriate values in ALS were 20%, 15%, 8%, resp. In the "disease controls" a high antibodies titer was a rare finding. CONCLUSIONS It is concluded that in some ALS cases and also in some patients with other motor neuron diseases an autoimmune mechanism may contribute to motor neuron injury.