Amyotrophic lateral sclerosis(ALS) is progressive, degenerative, fatal disease of the motor neuron. No efficacious therapy is available to slow the progressive loss of function, but several new approaches including neurotrophic factors, antioxidants and glutamate antagonists, are currently being evaluated as potential therapies. Mortality, and/or time to tracheostomy, muscle strength and pulmonary function are used as primary endpoints in clinical trials for treatment of ALS. The effect of new therapies on the quality of patients' lives are also important, so we sought to develop a rating scale to measure it. The revised ALS Functional Rating Scale(ALSFRS-R), which has addition of items to ALSFRS to enhance the ability to assess respiratory symptoms, is an assessment determining the degree of impairment in ALS patients' abilities to function independently in activities of daily living. It consists of 12 items to evaluate bulbar function, motor function and respiratory function and each item is scored from 0(unable) to 4(normal). We translated the English score into Japanese one with minor modification considering the inter cultural difference. And we examined reliability of the translated scale. As a measure of reliability, the intraclass correlation coefficient(ICC) was evaluated for total score and the Kappa coefficient proposed by Cohen and Kraemer was calculated for each item. Moreover, we examined sensitivity to clinical change over time and carried out the factor analysis to analyze the factorial structure. The subjects were 27 ALS patients and each was scored twice for reliability or three times for sensitivity by 2 to 5 neurologists and if possible, nurses. The ICC for total score was 0.97(95% C. I.; 0.94-0.98). Extension of the Kappa coefficients were 0.48 to 1.00 for inter-rater reliability and the averaged Kappa coefficients were 0.63 to 1.00 for intra rater reliability, respectively. Concerning the factorial structure, the contribution of the first factor(the first principal component) were 53.5% principal factor solution. The factor loadings of items were 0.52-0.91 except "salivation" and this factor almost equal to the simple sum of all items was interpreted as the general degree of deterioration. The promax votation revealed the riginally supposed factor structure with 3 factors(groups of items): neuromuscuclar function, respiratory function and bulbar function. The rating scale correlated with Global clinical impression of change(GCIC) scored by neurologists and declined with time, indicating its sensitivity to change. On the bases of these results, ALSFRS-R(Japanese version) is considered to be highly reliable enough for clinical use.