The high prevalence of atherosclerosis in developed nations is not breaking news; it has been well established that heart disease is the leading cause of death in the United States, and it presents a major socioeconomic burden. Investigators across the globe have been laboring for decades to unravel the molecular mechanisms that contribute to atherosclerosis, and while some of the major players in these pathways have been identified, unanswered questions persist. Over the past ten years, an enormous amount of work has been done to establish the role of ATP-binding cassette (ABC) transporters in lipid trafficking, and their subsequent influence on the development of atherosclerosis. Two rare diseases have been identified as models for studying the effects of ABC transporter mutations on the progression of atherosclerosis: Tangier disease, which is caused by a mutation in ABCA1, and sitosterolemia, which occurs as a result of mutations in either...