The catecholamine dopamine (DA) plays a key role in the physiology of most vertebrate and invertebrate organisms. In addition to its role as a transmitter in the nervous system, it has a role in development. The relatively few DA neurons in the mammalian brain have important roles in many neural functions including fine motor integration, neuroendocrine hormone release, cognition, emotive behaviors, male sexual behavior and possibly memory. Considerable information has been accumulated on the complex mechanisms of midbrain patterning, dopamine phenotype induction and maturation and the role of epigenetic factors in speciation, development and maintenance of midbrain dopaminergic function. Among other issues, this book describes the molecular and morphological events required for the induction of the neural plate for the establishment of regional identities. Knowledge of the complex integrative functions exerted by dopamine on target cells has been promoted by the ! molecular characterization of the DA receptor gene family. The chapters collected in this book provide new and extensive information that will enable scientists to further their knowledge of the basic mechanisms underlying DA neuron development and function.