This is a review of recent research on world-systems. We cover studies of the current system and studies that compare the contemporary global system with earlier, smaller intersocietal systems. Research on the cycles and secular trends found in the modern world-system is discussed at length. This includes an examination of economic cycles of various lengths as well as their links with broader cycles like the rise and fall of hegemonic core powers, international financial crises, and the cycle of global war. We also survey recent studies of core-periphery hierarchy.