Neurodegenerative disorders represent a major class of disorders for which thus far any effective small molecule drug therapy has failed to emerge. RNA interference (RNAi), by which disease genes such as those identified for spino-cerebellar ataxia and Huntington's disease can be specifically silenced, has great potential in becoming a successful therapeutic strategy for these diseases. RNAi has shown therapeutic value in vitro and in animal disease models and clinical trials are currently on their way. However, there are problems, such as toxicity due to non-specific silencing, generation of immune responses and over-saturation of RNAi pathway components that must be overcome in order to establish RNAi as a safe and effective therapy. Current research on the endogenous roles of RNAi, through the action of microRNAs, has offered much knowledge to optimise the exploitation of RNAi.