The measurement and manipulation of cytosolic free Ca²⁺ permits the investigation of the mechanisms of generation of the Ca²⁺ signal and cellular responses to these Ca²⁺ signals within living neutrophils. The optical methods most applicable to neutrophils, which will be discussed here, are (1) the use of fluorescent indicators of Ca²⁺ and (2) photoactivation of reagents involved in Ca²⁺ signaling. Both of these synthetic agents can be loaded into neutrophils as lipid-soluble esters or can be microinjected into the cell. In this chapter, we will outline some of the techniques that have been used to monitor, visualize, and manipulate Ca²⁺ in neutrophils.