There has been significant increase in the knowledge and understanding of the etiology, pathogenesis, and treatment of inflammatory periodontal diseases over the past few decades. However, arriving at a diagnosis and determining the course of treatment still are based largely on basic clinical techniques, such as periodontal probing. With all the advances in dental technologies, the periodontal probe remains the best diagnostic tool to collect information regarding the health status and attachment level of periodontal tissues, despite some inherent drawbacks, especially when it is used to monitor periodontal status longitudinally. Dental clinicians must be aware of the strengths as well as the limitations of using a periodontal probe to gather data. This systematic review describes several factors that affect the accuracy and reliability of periodontal probing, including periodontal health, probing force, type of periodontal probe, and probing site.