This article illustrates a technique that can help public safety officers quickly identify the timing and cause of changes in incident rates and help explain to public management and other government officials the effect of new policies and changing conditions. The use of control charts, developed by Shewart at Bell Labs for use extensively by the military during World War II, has the ability to find trends of incidents, measure the effect of new policies on incident calls, and to compare the quantity of incident calls against a historical baseline. They provide a handy visual representation of the variation in incident calls over a period of time. This article describes the use of control charts by first describing the four basic steps to drawing and analyzing a control chart. It also discusses the benefits of control charts in finding trends in crime and measuring the effect of policing methods.