The problem of allocating indivisible objects to different agents, where each individual is assigned at most one object, has been widely studied. Pápai (2000) shows that the set of strategy-proof, nonbossy, Pareto optimal and reallocation-proof rules are hierarchical exchange rules -generalizations of Gale's Top Trading Cycles mechanism. We study the centralized allocation that takes place in multiple markets. For example, the assignment of multiple types of indivisible objects; or the assignment of objects in successive periods. We show that the set of strategy-proof, Pareto efficient and nonbossy rules are sequential dictatorships, a special case of Pápai's hierarchical exchange rules.JEL classification: C78, D61, D78, I20.