Mast cells are activated by a number of agents that act independently from immunoglobulin E (IgE)-mediated hypersensitivity. One of these agents is oxidized low-density lipoprotein (oxLDL). OxLDL has been implicated in the pathogenesis of atherosclerosis and has been shown to induce microvascular dysfunction by the activation of mast cells. In this chapter, we describe the method for isolation of human LDL, oxidation of LDL, and demonstrate that oxLDL activates mast cells by measuring messenger ribonucleic acid (mRNA) levels and protein levels of interleukin (IL)-8 an inflammatory cytokine. IL-8 is a potent chemoattractant for neutrophils and monocytes, which would result in a chronic inflammatory response. IL-8 mRNA levels were measured by reverse-transcription polymerase chain reaction and protein levels by enzyme-linked immunoassay.