Niemann-Pick C1 (NPC1) disease is characterized by cholesterol accumulation in lysosomes and aberrant feedback regulation of cellular cholesterol homeostasis. The gene responsible for the disease is NPC1, which encodes a protein with five transmembrane domains. NPC1 protein has homology with the resistance-nodulation-division (RND) family of prokaryotic permeases and may normally function as a transmembrane efflux pump. NPC1 uses a proton motive force to remove accumulated acriflavine from the endosomal/lysosomal (E/L) system. NPC1 can function to transport lipophilic molecules but not cholesterol, out of the E/L system. The fact that NPC1 can transport acriflavine and fatty acids suggest that this permease may have a “multidrug” transport function, part of which is its housekeeping role in cellular cholesterol homeostasis. Expression of NPC1 in E. coli facilitated the transport of acriflavine across the plasma membrane, causing cytosolic accumulation and resulting in transport of oleic acid, but not cholesterol-oleate across the plasma membrane, establishing NPC1 as a eukaryotic member of the RND permease family.