Progress in molecular investigations presents new data facilitating the recognition of pathogenic mechanisms of numerous nervous system diseases, among them amyotrophic lateral sclerosis (ALS). Molecular studies of ALS are mainly concentrated on genetic search, excitotoxicity and astrocytic participation, pathology of neurofilaments, apoptosis, trophic factors, and selective motoneurone degeneration. In literature part of the results of these investigations are presented as certainty but some doubts exist. Problems of the role of the superoxide dismutase (SOD-1) mutation gene and free radical scavenging and selective vulnerability and death of motor neurone cells in ALS are mentioned.