Polyglutamine neurodegenerative disorders are characterized by the expansion of a glutamine tract within the mutant disease-causing protein. Expression of the mutant protein induces a progressive loss of neuronal function and the subsequent neurodegeneration of a set of neurons characteristic to each disease. Spinocerebellar ataxia type 1 (SCA1) is one polyglutamine disease where various experimental model systems, in particular transgenic mice, have been utilized to dissect the molecular and cellular events important for disease. This review summarizes these findings and places them in a context of potential future research directions. (C) 2000 Academic Press.