Background: There is an increasing interest in the impact of clinical guidelines on improving the quality of asthma treatment. As a consequence many recommendations for the treatment of asthma for health care professionals have been distributed under the label "clinical guidelines" during recent years in the western world. Their methodical quality ranges from very low to very good, because many of them don't use an explicit and sensible process to identify, select and combine evidence. Objectives: The objective was to assess the quality of German guidelines for the treatment of asthma in relation to guidelines from other countries, with emphasis to the evidence base.

Methods: In order to distinguish between evidence-based and non evidence-based guidelines we collected guidelines from countries with a comparable genetic, social and medical background. According to the ideas of evidence-based medicine, we used and partly developed critical appraisal criteria for clinical guidelines and assessed the validity of the collected guidelines by applying those criteria.

Results: We assessed the compliance of thirteen national and international guidelines with the criteria. Only two of the guidelines (Scottish Intercollegiate Guidelines Network and Canadian Association of Emergency Physicians / Canadian Thoracic Society) described how and when evidence was gathered, selected, synthesised and combined the recommendations with the corresponding level of evidence. There were also big differences between the appraised guidelines, concerning most of the other criteria like multiprofessional development, documentation of objectives, outcomes, benefits, harms, costs, sponsors.

Conclusions: In the future guidelines for the treatment of asthma must be developed in a more transparent process, to allow the practitioner to make informed decisions about asthma management on the bases of the available evidence. A cooperation with the Agency for Quality in Medicine, K ln, Germany