This chapter focuses on mean, abusive, and disruptive (MAD) behavior of medical professionals in the workplace. MAD behavior subverts the ethical obligation of healthcare professionals from consistently placing the interests of the patient foremost, by interfering with the normative processes of collegiality, cooperation, communication, and teamwork. MAD behavior encompasses an extreme degree of uncivil and unprofessional demeanor. It violates ethical standards of practice and impedes patient safety and quality improvement. MAD behavior's harmful impact on workplace staff increases the risk for substandard care and adverse patient consequences. MAD behavior is a manifestation of a personality disorder that is characterized by maladaptive behavior and lack of personal insight. In order for MAD physicians to continue to practice, they must be strictly be held to exert a sufficient degree of control over their behavior that precludes their adversely impacting the culture of safety.