The complicated and expensive diagnostic apparatus available today has to be applied in an orderly sequence. This order depends on certain prerequisites, e.g. on the disease, urgent complications, patient tolerance, apparatus potential, hospital structure and organisation etc. The more rational the indication is to use certain methods, the more efficient will be the results. The appropriate concepts and suggestions for certain general and specific examples, used by us at present are demonstrated. Complicated and expensive diagnostic procedures have to be decided primarily on an interdisciplinary level. The increased costs of these procedure are balanced by a decrease in hospital stay and fewer operative explorations too. At other places different actions will be taken for equally good reasons.