In 1956, Stella Chess and Alexander Thomas launched the pioneering New York Longitudinal Study, a systematic investigation into the concept of temperament that has been pursued to the present decade. The findings from this study - that temperamental profiles of infants, children, adolescents, and adults show specific individual behavioral characteristics - are accepted as basic to the psychological mechanism of behavioral functioning. Now, these preeminent authorities and teachers in the field of child and adolescent psychiatry present a distinguished introduction to their internationally recognized work. This volume takes the reader from concept - including the definition of temperament and the studies that support and expand upon that definition - to specific explorations of temperament and its impact across various practice settings and special populations.