Primary cilia are membrane-bound microtubule-based structures present on most mammalian cells and are important for intercellular signaling. Cilia are present on a subset of endothelial cells, which form the innermost layer of blood vessels, where they project into the vessel lumen and are implicated as mechanical sensors of blood flow. To test the in vivo role of endothelial cilia, I conditionally deleted Ift88, a gene required for ciliogenesis, in endothelial cells of mice. I found that endothelial primary cilia are dispensable for vascular development. Removing endothelial cilia increased atherosclerosis in Apoe-/- mice fed a western-type diet, indicating that cilia protect against atherosclerosis. Consistent with this result, Apoe-/- mice lacking endothelial cilia had increased inflammatory gene expression.