The supervision of a domestic health system in the context of the trade environment in the 21st century needs a sophisticated understanding of how trade in health services affects, and will affect, a country's health system and policy. This notion places a premium on people engaged in the health sector understanding the importance of a comprehensive outlook on trade in health services. However, establishment of systematic comparative data for amounts of trade in health services is difficult to achieve, and most trade negotiations occur in isolation from health professionals. These difficulties compromise the ability of a health system to not just minimise the risks presented by trade in health services, but also to maximise the opportunities. We consider these issues by presenting the latest trends and developments in the worldwide delivery of health-care services, using the classification provided by the World Trade Organization for the General Agreement on Trade in Services. This classification covers four modes of service delivery: cross-border supply of services; consumption of services abroad; foreign direct investment, typically to establish a new hospital, clinic, or diagnostic facility; and the movement of health professionals. For every delivery mode we discuss the present magnitude and pattern of trade, main contributors to this trade, and key issues arising.