A novel method utilizing the BD Oxygen Biosensor System has been developed to rapidly, simply, and accurately determine the growth rate of microorganisms in broth, with no needfor plate counts, standardized inocula, or technically difficult manipulations. The BD Oxygen Biosensor System incorporates an oxygen-sensitive material into the wells of standard Falcon microplates. The time response of this sensor monitored in afluorescence plate reader can be used to quantitate microbe growth. The method entails seeding a dilution series of microorganism onto the plate and reading at regular intervals for 3-10 h. As the organisms grow and consume oxygen, thefluorescence intensities increase over time to form a family of sigmoidal growth curves. A simple mathematical analysis of the time intervals between the curves yields the doubling time, which is independent of the initial concentration of organism. The method is ideally suited as a screening tool for assessing the impact of culture conditions, media composition, or added compounds on growth kinetics.