The purpose of this chapter is to present some basics as regards the energy efficiency of ships, including related regulatory activity at the International Maritime Organization (IMO) and elsewhere. To that effect, the Energy Efficiency Design Index (EEDI) is first presented, followed by a discussion of Market Based Measures (MBMs) and the recent Initial IMO Strategy to reduce greenhouse gas (GHG) emissions from ships. The discussion includes commentary on possible pitfalls in the policy approach being followed.