Global short-term medical volunteerism is growing, and properly conducted, is a tool in the fight for greater global health equity. It is intrinsically "ethical" (i.e., it involves ethics at every step) and depends upon ethical conduct for its success. At present, ethical guidelines remain in their infancy, which presents a unique opportunity. This paper presents a set of basic ethical principles, building on prior work in this area and previously developed guidelines for international clinical research. The content of these principles, and the benchmarks used to evaluate them, remain intentionally vague and can only be filled by collaboration with those on-the-ground in local communities where this work occurs. Ethical review must additionally take into consideration the different obligations arising from the type of institution, type of intervention, and type of relationship involved. This paper argues that frequent and formalized ethical review, conducted from the beginning with the local community (where this community helps define the terms of debate), remains the most important ethical safeguard for this work.