Research traditions studying multiunit systems include the multimarket perspective, which has used commitment and mutual forbearance theory, and the multiunit perspective, which has used learning and knowledge transfer theory. These perspectives are interdisciplinary, but to date there has been little direct interaction among them. Although this has been useful for their early development, it is now time that they join forces for further theory development in areas including; examining how variation in firm capabilities affects the coordination of branches and thus their forbearance or transfer of routines; bridging theories of market conduct and internal behavior to explore how knowledge about markets and competitor behavior is transferred among organizational units; making a theory of contingent multiunit or single-unit competitive advantage that can account for the continued coexistence of these organizational forms in many markets; examining the effects of firm contacts in alliances or technological fields on their competitive behaviors. The recent growth of research on multiunit organization and multimarket strategy in IO economics, strategic management and organization theory is very impressive, and suggests that such challenges will soon be tackled. We bring contributions from these research traditions together in a single volume to foster an interchange of ideas and findings among the volume's contributors and with readers and researchers in the field.