Lymphatic vessels are essential for lipid absorption and transport. Despite increasing numbers of observations linking lymphatic vessels and lipids, little research has been devoted to address how dysregulation of lipid balance in the blood, ie, dyslipidemia, may affect the functional biology of lymphatic vessels. Here, we show that hypercholesterolemia occurring in apolipoprotein E-deficient (apoE(-/-)) mice is associated with tissue swelling, lymphatic leakiness, and decreased lymphatic transport of fluid and dendritic cells from tissue. Lymphatic dysfunction results in part from profound structural abnormalities in the lymphatic vasculature: namely, initial lymphatic vessels were greatly enlarged, and collecting vessels developed notably decreased smooth muscle cell coverage and changes in the distribution of lymphatic vessel endothelial hyaluronic acid receptor-1 (LYVE-1). Our results provide evidence that hypercholesterolemia in adult apoE(-/-) mice is associated with a degeneration of lymphatic vessels that leads to decreased lymphatic drainage and provides an explanation for why dendritic cell migration and, thus, immune priming, are. compromised in hypercholesterolemic mice. (Am J Pathol 2009, 175:1328-1337; DOI. 10.2353/ajpath.2009.080963)