Although the usefulness of making a formal diagnosis in helping an individual deal with his/her 'problems' continues to be debated in all areas of medicine--"Il n'y a pas de maladies; il n'y a que des malades"--it is generally accepted that the initial interaction between doctor/healer/therapist and patient/client will consist of an attempt to fit the problem into one or more categories, to develop a diagnostic formulation. In the search for specificity and scientific accuracy increasingly sophisticated methods of selecting criteria have been developed to allow the assignment of a diagnosis. Examples will be given that even in the field of general medicine, a hierarchy of certainty versus uncertainty has to be accepted if potentially dangerous diagnostic errors are to be avoided. A similar approach has been proposed as a means of improving the decision making process in psychiatry. In the course of an epidemiological investigation into the prevalence of psychopathology among residents of longterm institutions, a simplified categorization into certain or suspected diagnoses is described. A semi-structured screening interview was developed for the study and will be discussed.