The academic study and the applied use of agent-based modelling of social processes has matured considerably over the last thirty years.The time is now right to engage seriously with the ethics and responsible practice of agent-based social simulation.In this paper, we first outline the many reasons why it is appropriate to explore an ethics of agent-based modelling and how ethical issues arise in its practice and organisation.We go on to discuss different approaches to standardisation as a way of supporting responsible practice.Some of the main conclusions are organised as provisions in a draft code of ethics.We intend for this draft to be further developed by the community before being adopted by individuals and groups within the field informally or formally.