Prostaglandin (PG) D is formed by two distinct PGD synthases (PGDS): lipocalin-type PGDS (L-PGDS), which acts as a PGD-producing enzyme and as extracellular lipophilic transporter, and hematopoietic PGDS (H-PGDS), a glutathione-S-transferase. PGD plays an important role in the maintenance of vascular function; however, the relative contribution of L-PGDS- and H-PGDS-dependent formation of PGD in this setting is unknown. To gain insight into the function played by these distinct PGDS, we assessed systemic blood pressure (BP) and thrombogenesis in L-Pgds and H-Pgds knockout (KO) mice. Deletion of L-Pgds depresses urinary PGD metabolite (PGDM) by ∼35%, whereas deletion of H-Pgds does so by ∼90%. Deletion of L-Pgds, but not H-Pgds, elevates BP and accelerates the thrombogenic occlusive response to a photochemical injury to the carotid artery. HQL-79, a H-PGDS inhibitor, further depresses PGDM in L-Pgds KO mice, but has no effect on BP or on the thrombogenic response. Gene expression profiling reveals that pathways relevant to vascular function are dysregulated in the aorta of L-Pgds KOs. These results indicate that the functional impact of L-Pgds deletion on vascular homeostasis may result from an autocrine effect of L-PGDS-dependent PGD on the vasculature and/or the L-PGDS function as lipophilic carrier protein.