The human rectum is present in the lower gastrointestinal tract and functions as a temporary storage site for fecal material. Endothelial cells in the rectum line the interior surface of the blood vessels and form the interface between intravascular and extravascular compartments. They limit the passage of cellular and soluble substances between the blood vessels and the tissues. Endothelial cells also play critical roles in angiogenesis, vasculogenesis, and the inflammatory response. Human Rectal microvascular endothelial cells (HRecMEC) play roles in the progression of rectal cancer. HRecMEC are useful tools to elucidate the mechanisms of angiogenesis and also to develop treatments for rectal cancer.