For some coronal mass ejections (CMEs), their interaction with the ambient solar wind can produce a forward-reverse shock pair. The high-speed mass ejecta compresses the plasma near the top of the CME on both sides of the tangential discontinuity which separates the CME plasma from the ambient solar wind plasma. The front of the compressed CME plasma propagates in the reverse direction relative to the ejecta flow, it may steepen to form a reverse slow shock. The front of the compressed solar wind plasma also propagates in the foward direction relative to the ambient solar wind and it may steepen to form a forward shock. The forward-reverse shock pair associated with CMEs moves outward in interplanetary space and evolves into a pair of fast shocks. The interplanetary manifestation of some CMEs is pictured as a magnetic cloud accompanied by a shock pair: a forward shock precedes the cloud and a reverse shock either within or behind the cloud. ¿ American Geophysical Union 1988