We examined 8 cases of familial ALS (amyotrophic lateral sclerosis) in three different families from our province, admitted to our hospital between 1970 and 1989. Clinical criteria for diagnosis were satisfied in all cases; EMG was performed in 6 out of 8 patients. 4 cases showed classical onset and 4 cases bulbar onset. The average age at onset was 65.7 + 10.6 years. The average survival was 19.1 + 9.2 months. In two families two generations were affected, in the other only one. The mode of transmission was found to be autosomal dominant with variable penetrance. Neither environmental nor toxic factors seemed to be involved in the development of the illness. Genetic investigations may help to elucidate the pathogenesis of familial ALS.