The incidence of amyotrophic lateral sclerosis (ALS) in Israel was determined for the period 1959 through 1974. A total of 246 patients with ALS was ascertained. The male-female ratio was 1.62:1. The average annual age-adjusted incidence per 100,000 persons increased during this period by 41%. The increase was almost entirely due to a higher rate in persons more than 60 years of age and was greater in women than in men. This led to a decrease in the male-female ratio. The mean age of onset increased from 52.8 to 58.6 years during the same period. The increment in incidence could not be explained by better case ascertainment or increased life expectancy, but greater precision in diagnosis of ALS in the aged may have partially contributed to the increase.