In recent years, the term "conformational disease" has been used to describe a range of disorders which are linked to misfolding and aberrant structural change in proteins. The molecular bases underlying the pathogenesis of neurodegenerative diseases are gradually being disclosed, and almost all of the diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease and prion disease are increasingly being realized to have common molecular mechanisms including the accumulation of misfolded or aggregation-prone proteins, thus, they can be termed "neurodegenerative conformational disease". There is now increased understanding of the molecular pathways involved in protein misfolding and aggregation and cellular toxicity in neurodegenerative conformational diseases. These are leading to approaches toward rational therapeutics.