The idea for this book developed during the course of several discussions among the editors while we were working together as staff scientists in the laboratories of the Clinical Neuro science Branch of the National Institute of Mental Health. It was a happy coincidence that the three of us, child psychiatrists with predominantly clinical interests, selected a collaborative bench research project involving neurotransmitter receptor characterization and regulation. We appreciated the relevance of our work to child psychiatry and wished for a forum to share the excitement we enjoyed in the laboratory with our clinical colleagues. Moreover, it seemed to us that much of the pharmacological research in child psychiatry proceeded on an empirical basis, often without a compelling neurochemical rationale. This could reflect the paucity of neurochemical data that exists in child psychiatry and the very limited understanding of the pathophysiology in most psychiatric disorders that occur in childhood. Also, we bemoaned the fact that there was a virtual absence of meaningful interchange between clinical investigators in child psychiatry and their colleagues in the neurosciences. We believed that an edited book appealing to clinicians and basic scientists could serve as an initial effort to foster interchange between them. The editors wish to emphasize that this book is viewed as only a beginning in the process of interchange that must take place.