While there has been much work on finding and developing top performers in the workplace, less attention has been focused on how to manage those workers who are harmful to organizational performance. In the most dramatic form, such workers can generate enormous regulatory and legal liabilities for the firm, harm its reputation, and invalidate its corporate social responsibility program. We explore a large dataset of over 50,000 workers across 11 different firms to document a variety of aspects of workers characteristics and circumstances that lead them to engage in actual "toxic" behavior. We also find that removing a toxic worker or converting him into an average worker enhances organizational performance to a much greater extent than replacing an average worker with a superstar worker.