Evidence that a health practitioner, on some other occasion, engaged in conduct similar to the conduct alleged in current disciplinary proceedings, is both prejudicial to the practitioner and potentially highly probative. The admissibility of such evidence (usually referred to as "tendency evidence") is highly prescribed in criminal and civil court proceedings pursuant to statutory rules and common law cases. These rules attempt to achieve a reasonable balance between prejudicial effect and probative value. However, tribunals are not bound to follow rules of evidence and tribunal disciplinary proceedings have different objectives and functions than court proceedings. Further, it has generally been understood that tribunals are not expected to make complex legal rulings concerning the admissibility of disputed evidence. There is some evidence that national boards are becoming more willing to attempt to adduce tendency evidence in cases involving sexual misconduct on the part of health practitioners. This article examines how tribunals have dealt with applications by national boards to adduce tendency evidence and how such evidence is used by tribunals given that tribunals are not bound to follow statutory rules of evidence which apply in the courts.