In 1902, Albert Moll, who at that time ran a private practice for nervous diseases in Berlin, published his comprehensive book on medical ethics, Ärztliche Ethik. Based on the concept of a contractual relationship between doctor and client, it gave more room to the self-determination of patients than the contemporary, usually rather paternalistic, works of this genre. In the first part of the present paper this is illustrated by examining Moll’s views and advice on matters such as truthfulness towards patients, euthanasia, and abortion. The second part of this article discusses how Moll engaged with the then publicly debated issues of experimentation on hospital patients and the ‘trade’ of foreign private patients between agents and medical consultants. In both matters Moll collected evidence of unethical practices and tried to use it to bring about change without damaging his or the profession’s reputation. However, with his tactical manoeuvres, Moll made no friends for himself among his colleagues or the authorities; his book on ethics also met with a generally cool response from the medical profession and seems to have been more appreciated by lawyers than by other doctors.