In conclusion, the microtiter system has several advantages over conventional broth dilution methods. It is more rapid to set up, economical in its use of media and materials, and many more strains can conveniently be tested on the same occasion and under the same conditions, giving better comparability. Microtitration is almost as reproducible as large-tube dilution, and certainly adequately so for all laboratory and clinical purposes. Minimal bactericidal concentrations can be determined by microtitration, unlike agar plate dilution, and the system is readily adaptable to the measurement of antibiotic concentrations in body fluids where the accuracy can be increased if required (12) by the incorporation of an intermediate dilution series. Overnight incubation is, however, necessary and so rapid results are not possible.