The D3 dopamine receptor is a member of the family of D2-like dopamine receptors. Since the cloning and identification of the D3 receptor in 1990, considerable progress has been made towards understanding the function of this novel site. Although some avenues of investigation have yielded more definitive results than others, studies to date indicate the D3 receptor is localized preferentially in limbic brain areas and affects locomotion and perhaps reinforcement and reward. A subpopulation of the receptors appear to be autoreceptors which modulate dopamine synthesis, release, and neuronal activity. These observations have led to the hypothesis that the D3 receptor may be an appropriate target in the treatment of neuropsychiatric disorders such as schizophrenia and drug addiction. The role of D3 sites in disease, however, remains to be established. Genetic association of D3 receptor polymorphisms with neuropsychiatric disorders have been proposed. Alterations in expression of D3 sites may occur in some diseases. Although the study of this receptor is clearly in the early stages, these findings lay the foundation for future investigation. In this review, dopamine D3 receptor brain localization, cellular signaling mechanisms, and associated behavior will be discussed. The potential role of the D3 site in neuropsychiatric disorders and as a therapeutic target is also addressed.