Riluzole is the only therapy proven in clinical trials to prolong amyotrophic lateral sclerosis (ALS) survival (approximately three months). Questions remain concerning riluzole's effectiveness in everyday practice, the appropriate duration of treatment, which certain subtypes of ALS specifically benefit from the medication, and whether early administration prolongs survival in ALS patients. We report the results of a population-based outcome study of riluzole in the Irish ALS population over a five-year period. Using data from the Irish ALS Register, we examined the survival of patients diagnosed with ALS between 1 January 1996 and 31 December 2000 who attended a general neurology clinic (n = 264 patients, MD = 16). An intention to treat analysis is employed. 149 (61 %) patients were prescribed riluzole and the remaining 99 (39 %) were not. Riluzole therapy reduced mortality rate by 23 % and 15 % at 6 and 12 months respectively and prolonged survival by approximately four months. This beneficial effect was lost in prolonged follow-up. Suspected or possible ALS patients receiving riluzole experienced similar improvement in survival as the overall cohort. Survival benefit was more marked among patients with bulbar-onset disease. Multivariate analysis did not show riluzole to be an independent predictor of survival. We conclude that riluzole therapy improves ALS survival in everyday clinical practice by a short period of time. This beneficial effect is transient and stopping the medication in advanced ALS should be reconsidered. Bulbar-onset patients appear to particularly benefit from riluzole for unclear reasons. Our initial observations support riluzole use in early ALS.