Variation in outcome is a natural result from any complex biological or production process. Unfortunately, this variation can cloud our decision making and lead us to take inappropriate action. The control chart is a basic quality management tool that helps managers and clinicians make statistically sound decisions when analyzing outcome data from processes. In this tutorial, we will illustrate the problems inherent in taking action based on data that displays variation. We will then develop the statistical foundation for control charts and show an example of its use to analyze data from a pharmacy process.