An epidemiological investigation of 41 subjects with amyotrophic lateral sclerosis observed in the Province of Messina during 1976-1985 was performed. The incidence was 0.61/100,000 and the prevalence 2.48/100,000 inhabitants. The illness was found to be prevalent in males. The atrophic type occurred in 17 subjects, the bulbar type in 23 cases and the pseudo-polyneuritic form in only one patient. The mean age on the onset was 57.29 +/- 10.55 years. The duration of the illness was significantly higher in patients with atrophic type (p less than 0.01). No significant difference between occupation and development of the disease was found. Among all patients 12.19% presented evidence of trauma, but traumatic events were equally present in a control group.