The amyotrophic lateral sclerosis (ALS) severity scale has been developed to provide an ordinal staging system and a means of rapid functional assessment for patients with ALS. The scale allows an examiner to evaluate the symptoms of ALS numerically in four categories that describe speech, swallowing, lower extremity, and upper extremity abilities. These scores, combined with a vital capacity measured on a hand-held respirometer, provide a rapid, accurate assessment of a patient's disease status and can be used for treatment planning. The ALS severity scale has been shown to have an average estimated reliability coefficient of 0.95 between examiners. Speech ratings were correlated greater than 0.80 for objective speech measures. Rates of progression of the total score in a small group of patients ranged from -3.4 to -24.0 points/year with a mean of -11.3 points/year.