Early-onset torsion dystonia is a hyperkinetic movement disorder caused by a deletion of one glutamic acid residue in torsinA, a novel member of the AAA-family of ATPases. No mutation has been found so far in the closely related torsinB protein. Little is known about the molecular basis of the disease, and the cellular functions of torsin proteins remain to be investigated. We generated polyclonal anti-peptide antibodies directed against human torsinA and torsinB proteins. In Western blot analysis of mouse brain homogenates, the antibodies specifically recognized 33 kDa endogenous torsinA and 52 kDa endogenous torsinB. Absorption controls showed that labeling was blocked by cognate peptide used for immunization. Immunolocalization studies revealed that torsinA and torsinB were widely expressed throughout the mouse central nervous system. Both proteins were detected in the majority of neurons in nearly all regions. The proteins displayed cytoplasmic distribution, although in some types of neurons localization was perinuclear. Strong labeling of neuronal processes and fibers was detected for both proteins. TorsinA and torsinB have similar CNS distribution, although some differences were observed. Widespread expression suggests that these proteins may play an essential role in normal neuronal functions. The localization of torsinA and torsinB immunoreactivity in neuronal processes points to a potential role for torsin proteins in synaptic functioning.