Electroencephalography (EEG) has been used to investigate cortical mechanisms involved in pain, to diagnose pain conditions, and to monitor therapeutic outcomes. The purpose of this systematic review is to determine if EEG has been validated for use in the investigation of the mechanisms, diagnosis, and monitoring of therapeutic indices involving changes in chronic pain. Materials and Methods: A literature search was conducted of Embase, Medline, PubMed, Web of Science, and Scopus databases using the search keywords chronic, pain, and EEG, from all publication dates. This review includes only publications in English, and studies done on human subjects. Randomized Controlled Trials (RCTs) were included in the final sample if they displayed data involving both EEG and chronic pain in their abstracts. Results: 1150 articles were screened. After elimination of duplicates 242 studies were identified as uniquely fulfilling the search characteristics, 9 RCTs, 100 controlled observational studies, and 132 case studies or series. There was heterogeneity in the assessment and types of chronic pain conditions studied, the therapeutic interventions used, the sleep/wake state of the subjects, the pain measurements and the EEG outcomes assessed. Discussion: Most of the studies used had methodological issues relating to bias and sample size which make it difficult to draw definite conclusions about the utility of EEG in a clinical patient population with chronic pain. Conclusion: More high quality RCTs are required to investigate the role of EEG in the diagnosis and therapy of chronic pain conditions.