ABSTRACTThe health-related quality of life (HRQoL) is assessed using instruments that have been validated scientifically. From the viewpoint of assessment, they are different from other clinical indices because the subjects themselves evaluate their own HRQoL (the patients in many clinical settings). As an index for evaluating health care services or outcomes, the HRQoL is as important as life expectancy. These instruments can be classified into generic and disease-specific instruments. There are numerous disease-specific instruments that can be used for patients with asthma, such as Juniper et al.'s Asthma Quality of Life Questionnaire (AQLQ), the Living with Asthma Questionnaire (LWAQ), the St. George's Respiratory Questionnaire (SGRQ), and Marks et al.'s Asthma Quality of Life Questionnaire (AQLQ). The characteristics of each instrument should be considered in the selection of specific HRQoL questionnaires for clinical research. Generally, the HRQoL is more disturbed in patients with severe asthma, and has been considered to be an important end-point in randomized controlled trials that involve asthma patients. We expect that further studies will also be performed in Japan.