Just as health is characterized primarily by the absence of disease, welfare can be characterized partly by the absence of abnormal behaviour or behaviour problems. Consequently, just as treatment and prevention of disease improves health, treatment and prevention of behaviour problems can improve welfare. The purpose of developing a discipline termed [`]clinical ethology' is to apply the same procedures and principles used in medicine to the area of ethology. Briefly, these procedures consist of searching for specific symptoms of a disease, partly through a clinical examination and partly by conducting specific diagnostic tests, the results of which point to a specific diagnosis. Based on the diagnosis, suggestions for treatment as well as preventive measures are given. Application of clinical procedures to the treatment and prevention of behaviour problems reveals some areas that need improvement. One such area concerns the diagnostic process, i.e. the search for specific symptoms of the various problems through behaviour observations and behaviour tests. Another area concerns the treatment of behaviour problems, something that primarily is done in companion animals and in horses and less so in farm animals. A third area concerns the prevention of behaviour problems, an area that despite much attention still needs refinement, before exact recommendations can be given to the client. As many behaviour problems are related to the way people house and handle domestic animals, possibly the most important aspect of clinical ethology is its focus on the human-animal interaction, to subject this interaction to systematic investigation, and to include it both in the diagnostic, the therapeutic, and the preventive part of the clinical process. Developing a discipline of [`]clinical ethology' could (I) improve the welfare of domestic animals in a way that is perceived by animal owners as a professional help based on scientific knowledge and (II) stimulate ongoing research by emphasizing the therapeutic and preventive aspects of solving behaviour problems in farm and companion animals. In addition, such a development could (III) create new jobs for [`]behaviour practitioners'.