Neuroprotective effects of several bile acids are well documented in a wide range of neurodegenerative diseases, including AD, PD, ALS, HD, and retinal degeneration, in cellular and animal models and in human clinical trials. Due to the historical precedent set by the use of bear bile in ancient Chinese medicine, the majority of the studies have focused on UDCA and its derivatives. However, bile acids are a relatively large group of structurally related molecules, thus little is known about the potential efficacy of other bile acid species or the roles of circulating vs. endogenous bile acids synthesized within the central nervous system. In addition, most of the mechanistic studies have been centered on apoptosis and related pathways (Figure 2). However, essentially no data is available on the primary signaling pathways through which bile acids act, the cellular receptor TGR5 and the nuclear receptors FXR and RXRα, despite the well-known function of retinoic acid as a potent neurotrophic molecule. Determining the precise molecular mechanism(s) of neuroprotection by bile acids in neurodegenerative disorders will be important to realize their future therapeutic potential.