Is there a difference in the way family physicians and specialists deal with clinical problems? Family physicians, in contrast to specialists, work in a practice environment in which there is a high prevalence of symptomatic discomfort, but a low prevalence of frank disease. These circumstances result in clinical strategies that are very different to those used in secondary and tertiary levels of care, and which run counter to what are usually accepted as medical norms. The primary care physician must often diagnose what things are not, rather than what they are, must make management decisions prior to, or instead of, diagnostic decisions and must resist the temptation to be ;thorough' These imperatives are reflected in the language family physicians sometimes use in their conversations with patients. Clinical reasoning in primary care involves important but poorly understood intellectual processes which may be of significance to all levels of medicine.