This chapter examines the special ethical responsibilities of information systems professionals based on the fundamentals of ethics as commonly understood in the Western world. We start first with principles from religious texts and the codes of ethics included in them. We then examine codes of conduct promulgated by nonreligious institutions. We conclude that ethics is personal, situational and changes over time. Thus, it impossible to formulate codes of conduct that apply to all real life situations. We identify the special ethical responsibilities that information systems professionals face in their roles as custodians of information technology, as custodians of the information systems that use this technology and as custodians of the data and information that surround information systems. The situations we face from day-to-day as we deal with the ethical aspects of information systems will always require us to decide between ethical imperatives that are in conflict with one another.