This study concerns an analysis of the feasibility, validity, and repeatability of telephone interviews for the collection of data concerning health-related quality of life in asthma and patient reports of their use of asthma therapy. A computer-assisted hierarchical interview algorithm was developed that allowed rapid and precise recording of all aspects of asthma medication including drug, dose, and delivery system. This questionnaire was used together with the Symptoms and Impacts components of the St. George's Respiratory Questionnaire (SGRQ) in one face-to-face and then in three computer-assisted telephone interviews (CATIs) that took place 1, 3, and 13 weeks later. One hundred patients with asthma who had received inhaled steroids within the previous year were identified from general practice records. The intraclass correlation between the face-to-face interview and the first CATI for the SGRQ scores and the daily dose of inhaled steroid was approximately 0.8. For daily bronchodilator use, this value was 0.56. The intraclass correlation obtained between two CATIs 3 months apart was a little lower: SGRQ scores, 0.78; inhaled steroid dose, 0.67; bronchodilator use, 0.58. Telephone interviews can provide repeatable and efficient measurements of health and patient-reported drug use in asthma.