The term phantom chlorides is often used when refiners experience episodes of high unexplained chlorides that result in increased corrosion and fouling. Understanding the different types of chlorides helps begin the troubleshooting process of finding and addressing the root cause. Chlorides found in the refining industry are typically divided into two categories – inorganic and organic. In order to discover where in the refinery these chlorides have an impact these categories can also be further divided into extractable vs. non-extractable and hydrolyzable vs non-hydrolyzable. Through the use of case studies this paper will focus on troubleshooting techniques that can help identify the source of the phantom chlorides so that effective mitigation strategies can be developed.