We studied the cross-cultural Spanish adaptation of the Amyotrophic Lateral Sclerosis Assessment Questionnaire (ALSAQ-40) to assess the subjective health status in amyotrophic lateral sclerosis (ALS) patients. The ALSAQ-40 questionnaire was adapted and applied to 53 randomly selected ALS patients from different regions in Spain. Reliability assessment and factorial analysis were performed in order to determine the dimensions of the scale. The validation was carried out by means of comparing the ALSAQ-40 with two instruments usually used in the assessment of ALS patients--the Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS) and the McGill's Quality of Life Questionnaire (MQOL), comparing the latter with the emotional dimension of ALSAQ-40. This Spanish adaptation closely resembles the ALSAQ-40 although the emotional dimension is more heterogeneous and there are cluster-gathering Feeding and Communication dimensions. ALSAQ-40 and ALSFRS questionnaires showed a high correlation, as did the emotional dimension of ALSAQ-40 with the Psychological Symptoms, Life Expectancy, Meaningful Existence and the whole score of the MQOL. In conclusion, this Spanish adaptation of ALSAQ-40 is in accordance with the statistical results from the original English version.