[Rational diagnosis in pneumonology]

A survey is given of the rational use of diagnostic measures in pneumonology. Of the investigations following the anamnesis and the clinical findings (radiology, bacteriology, clinical chemistry, clinical immunology, electrocardiography, functional diagnostics, computed tomography) the radiological ones are most significant. Endoscopy is used in certain questions, in case that a diagnostic clarification could not be performed with the help of the simpler investigations. Rational diagnostics are always case-related, generalizations are only conditionally possible.