The electrical penetration graph (EPG) technique is a powerful tool for studying homopteran feeding behavior. The electronic monitoring equipment used by different research groups differs substantially, and experimental setups, data processing, and conclusions also show many differences. Specific problems related to the EPG technique often are overlooked during experiments. This chapter gives an overview of the possible uses, limitations, and pitfalls of EPGs and is meant to be a practical guide for experimental setups and analysis of results.