Abstract Fibromyalgia (FM) is a confusing and controversial diagnosis, characterized by widespread pain and tenderness at specific anatomical sites. The cause of this syndrome is unknown, and the course of the condition is difficult to predict. Without a known cause, predictable course, or effective treatment, it is not surprising that FM is a contentious diagnosis from a medical perspective, as well as a civil litigation and disability insurance industry perspective. The purpose of this study was to investigate judges' perceptions of credibility in litigated cases involving FM claims in the Canadian courts, and the relation between perceived credibility and awards granted. A systematic review was conducted of every trial-by-judge litigated FM claim in Canada ( N = 194 cases) up to 2003. The cases were examined in relation to credibility factors. The role and responsibility of the plaintiff was central in claims involving issues of misrepresentation, fraud, non-disclosure, failure to mitigate, and contributory negligence. The presence of these issues suggested a possible decrease or loss in the claim as a result of the plaintiff's conduct. In regards to the actions of defendants, the presence of investigative and surveillance information alone did not affect the awards granted. However, the credibility of that information had a large effect on the amount of award granted. Plaintiff credibility played a similar role, indicating that plaintiffs perceived as more credible were typically granted greater awards. An examination of medical expert credibility revealed that judges appear to perceive experts as more credible overall than plaintiffs, regardless of the expert's role in the case.