This chapter contains sections titled: Historical Notes: Tangier Disease (TD) and ATP-Binding Cassette Transporter 1 (ABCA1) The ABCA1 Gene and the Regulation of Its Expression The ABCA1 Protein and Its Interactions ABCA1: Mutations and Clinical Signs Targeted Inactivation and Overexpression of ABCA1 in Animal Models Liver and Macrophage ABCA1: Lipid Efflux and HDL Formation ABCA1 and Membrane Function ABCA1: Lipid Flop and Lipid Effl ux ABCA1 and the Lipid Microenvironment at the Membrane Conclusions Acknowledgments Abbreviations References