The control of dendritic cell (DC) migration is pivotal for the initiation of cellular immune responses. In this study, we demonstrate that the migration of human monocyte-derived (Mo) DCs as well as of ex vivo peripheral blood DCs toward CCL21, CXCL12, and C5a is stringently dependent on the presence of the proinflammatory mediator PGE 2, although DCs expressed CXCR4 and C5aR on their surface and DC maturation was accompanied by CCR7 up-regulation independently of PGE 2. The necessity of exogenous PGE 2 for DC migration is not due to the suppression of PGE 2 synthesis by IL-4, which is used for MoDC differentiation, because maturation-induced endogenous production of PGE 2 cannot promote DC migration. Surprisingly, PGE 2 was absolutely required at early time points of maturation to enable MoDC chemotaxis, whereas PGE 2 addition during terminal maturation events was ineffective. In contrast to mouse DCs, which exclusively rely on EP4 receptor triggering for migration, human MoDCs require a signal mediated by EP2 or EP4 either alone or in combination. Our results provide clear evidence that PGE 2 is a general and mandatory factor for the development of a migratory phenotype of human MoDCs as well as for peripheral blood myeloid DCs.