The permanently growing demands on clinic and laboratory constrain to considerations concerning a rational diagnostics. The spectrum of clinical interrogations which needs a clarification by laboratory diagnostics increases continuously. For the nephrologic diagnostics is again oriented to a step programme, which is adapted to the centrally published references to the development of a comprehensive system of the renal dispensary. It takes into consideration the possibilities of the diagnostics of the specialist for general medicine up to the subspecialist in a county hospital. As to the invasive diagnostics, particularly the renal biopsy, one must be reversed. This is indicated then, when from the result consequences would arise concerning the therapy to be performed or the choice calling etc.