This chapter describes two methods for measuring the bactericidal activity of neutrophils. These are a new simple fluorescence-based assay, which quantifies bactericidal activity by measuring changes in bacterial fluorescence associated with a loss of membrane potential over time, and a more traditional colony counting protocol. Two variations of these techniques are presented: a "one-step" protocol providing a composite measure of phagocytosis and killing, and a "two-step" protocol that allows calculation of separate rate constants for both of these processes.