Our objective was to determine the incidence and clinical-epidemiological characteristics of an ALS cohort patient in Catalonia (Spain). We conducted a population based registry for a three-year period (1999-2001) in Catalonia (6,361,365 inhabitants) using several sources of information. The original El Escorial diagnostic criteria (1994) for ALS were applied for the classification of patients. New cases diagnosed between 1 January 1999 and 31 December 2001 were 215 (118 males and 97 females), with an annual crude incidence rate of 1.4/100,000 (95% CI 1.3-1.8). This rate showed a peak age between 75 and 79 years. The incidence rate was 1.6 (95% CI 1.5-2.2) in males and 1.2 (95% CI 1.1-1.7) in females. Prevalence at the end of the period was 5.4/100,000 of the total population. Median age at onset was 64.3 years. Onset of symptoms was bulbar or generalized in 38% of cases. Mean disease duration at diagnosis was 11.0 months. Median time of survival from onset was 30.8 months. In conclusion, ALS incidence in Catalonia is within the range of other countries across Europe with different geographic, environmental and socioeconomic situations. However, as in other studies conducted in the Mediterranean area, Catalonia incidence is in the lower range of rates in Europe.