For about 25 years the association between occupational exposure to extremely low-frequency magnetic fields and the incidence of neurodegenerative diseases like Alzheimer's disease, Parkinson’s disease, amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS) has been examined with the help of epidemiological studies. Several studies are available on the prevalence and mortality of neurodegenerative diseases among workers, who were mainly employed at electrical utility companies. Several studies showed that occupational exposure to power-frequency magnetic fields is related to a higher risk of developing amyotrophic lateral sclerosis. The findings of studies on Alzheimer disease are inconsistent. There is only a weak evidence of association between extremely low frequency magnetic fields and Alzheimer disease. No association was found between occupational exposure and Parkinson’s disease. The Federal Office for Radiation Protection supported a research project (cf. Liebl et al. 2015) on the effects of extremely low-frequency electromagnetic fields on the development and progression of neurodegenerative diseases in experimental models with the purpose of verifying the results of the epidemiological studies and to reveal a possible mechanism of action.