My laboratory investigates the molecular and cellular mechanisms underlying two classes of human neurodegenerative disorders: prion diseases and Alzheimer’s disease. Alzheimer’s disease afflicts 5 million people in the U.S., a number that will increase dramatically as the population ages. Prion diseases are much rarer, but are of great public health concern because of the global emergence of bovine spongiform encephalopathy (“mad cow disease”), and its likely transmission to human beings. Moreover, prions exemplify a novel mechanism of biological information transfer based on self-propagating changes in protein conformation, rather than on inheritance of nucleic acid sequence. Prion and Alzheimer’s diseases are part of a larger group of neurodegenerative disorders, including Parkinson’s, Huntington’s and several other diseases, which are due to protein misfolding and aggregation. A prion-like process may be responsible for the spread of brain pathology in several of these disorders, and there is evidence that the prion protein itself may serve as a cell-surface receptor mediating the neurotoxic effects of multiple kinds of misfolded protein. Thus, our work on prion and Alzheimer’s diseases will likely provide important insights into a number of other chronic, neurodegenerative disorders.