Assessment of health-related quality of life (HRQoL) is relevant for the patients and is important in both clinical research and daily clinical practice. Generic and disease-specific instruments for assessment of HRQoL are reviewed. Changes in HRQoL provide important information on randomized controlled clinical trials as well as on observational studies. The floor effect is a limitation of many of the scales, especially in patients with less severe disease. Feasibility and low test-retest reproducibility limit the use of many of the instruments in clinical practice, especially when they are used for individual treatment decisions. Electronic transferral of data from patients to the health professionals by, for example, internet or a personal digital assistant (PDA), opens up new opportunities for frequent patient reports and improved access to the data.