There has been an increase in studies on amyotrophic lateral sclerosis (ALS) in the last thirty years. These studies show an ALS incidence rate that varies between 0.6 and 3.8 per 100,000 person-years. The incidence rate is significantly lower in Asia than in Europe and North America. ALS prevalence rates vary between 4.1 and 8.4 per 100,000. It is more common in men, and the male-to-female ratio is between 1 and 2. The mean age of ALS onset is between 51 and 66 years. Patients with familial ALS tend to have an earlier age of onset compared with patients with sporadic ALS. Some 58-82% of the cases have a spinal onset. The studies show age, male sex, and family history as risk factors. Other than these, lifestyle and exposure to environmental factors may have an effect. The period from the first symptoms to either invasive ventilatory support or death is between 24 and 50 months. ALS foci with high prevalence have been recorded in Guam, The Kii Peninsula, and New Guinea. Underdeveloped or developing countries show a speedy aging tendency, which points to an increased burden due to ALS in their future. Further epidemiologic studies with higher case numbers in different regions are needed to be able to enlighten causative associations of the disease.