International voluntary service (IVS) has a significant and growing presence worldwide. IVS is a policy and program tool used for international development aid, humanitarian relief, and promotion of international understanding. In the last century, forms of IVS have proliferated, while research on scope, effectiveness, and impacts has lagged behind. We propose a typology that addresses duration, nature of service, and degree of "internationality." Further, we identify IVS networks and support organizations that bolster the capacity of IVS sending and hosting organizations, and in this process create large and little recognized international institutions of cooperation. Building on the typology, we suggest program, policy, and research implications to advance knowledge of the role of IVS, its role in global civil society, and impacts it may have on human conditions and cross-cultural understanding.