Qualitative research may seem unscientific and anecdotal to many medical scientists. However, as the critics of evidence based medicine are quick to point out, medicine itself is more than the application of scientific rules.1 Clinical experience, based on personal observation, reflection, and judgment, is also needed to translate scientific results into treatment of individual patients.2 Personal experience is often characterised as being anecdotal, ungeneralisable, and a poor basis for making scientific decisions. However, it is often a more powerful persuader than scientific publication in changing clinical practice,3-5 as illustrated by the occasional series “A patient who changed my practice” in the BMJ.6

In an attempt to widen the scope of evidence based medicine, recent workshops have included units on other subjects, including economic analysis and qualitative research.7 However, to do so is to move beyond the discipline of clinical epidemiology that underpins evidence based medicine. Qualitative research, in particular, addresses research questions that are different from those considered by clinical epidemiology. Qualitative research can investigate practitioners' and patients' attitudes, beliefs, and preferences, and the whole question of how evidence is turned into practice. The value of qualitative methods lies in their ability to pursue systematically the kinds of research questions that are not easily answerable by experimental methods.

We use the example of asthma treatment to illustrate how qualitative methods can broaden the scope of evidence based medicine. Although there is consensus over evidence based practice in the treatment of asthma,8 questions remain about general practitioners' use of clinical guidelines and patients' use of prescribed medication.9