After some general considerations on the validity of antibiograms as a therapeutic guide, three methods are described and analyzed. Bacterial chemosensitivity to antimicrobic drugs were tested by the following methods: diffusion, dilution and automized methods. Only when transferred into routine laboratory methods that would reveal the results of chemosensitivity in quantitative values will a valid guide to antimicrobic chemotherapy be possible. Expressing chemosensitive bacteria directly in values of minimum inhibiting concentrations would evaluate the pharmokinetic action of single chemotherapeutical agents in relation to infective organ or apparatus pathologies which limits the practical significance of posology. Unfortunately, the collaboration between the clinical bacteriologist and the chemoterapist is still a long way off because of technical and laboratory difficulties delineating the pharmokinetic aspects in the use of the many chemoterapeutical agents in man.