Estimates in different countries of the number of disfunctioning doctors is around five per cent. The first part of this volume explores themes like the doctor as iatrogenic factor, the damage doctors may cause, the incompetent physician behind closed doors, the impaired physician, sexual contact between doctors and patients, and fraud and misconduct in medical science. The second part gives an overview of the problem doctor in different countries around the world and of the informal and formal mechanisms used to cope with this problem. The last part covers measures during training for preventing doctors from malfunctioning.