A case is reported of amyotrophic lateral sclerosis with occupational exposure to solvents and metals. The environmental toxin theory of motorneuron disease, including aspects of epidemiological, clinical, experimental and individual susceptibility is discussed. An overall evaluation of animal and human data was made using a methodological approach developed by the International Agency for Research on Cancer and a Scandinavian group of experts. It is concluded that there is a probable linkage between metals/solvents exposure and motorneuron disease.