This book outlines the basic tenets and applications of the theory of temperament based on the findings of the New York Longitudinal Study begun in 1956. It describes the concept and definition of temperament, reviews studies that support and expand on the definition, and explores temperament and its impact across various practice settings and special populations. The book is divided into two major sections dealing with basic concepts and new applications of the theory and practice of temperament. The chapters of the book are: (1) "Introduction," briefly outlining the historical context for the development of the theory; (2) "The Initial Concept of Temperament"; (3) "The Initial Hypothesis"; (4) The First Research Effort: From Failure to Success"; (5) The New York Longitudinal Study (NYLS)"; (6) "Analysis of Data and the Definition and Rating of Temperament and Categories"; (7) "The Clinical Interview for Temperament"; (8) "The Concept of Goodness of Fit"; (9) "Parent Guidance"; (10) "The Rapid Expansion of Temperament Practice and Theory Since 1970"; (11) "Parent and Child Education about Temperament"; (12) "Prevention and Early Intervention in Temperament Programs"; (13) "The Kaiser Permanente Temperament Program"; (14) "A New Mental Health Profession: The Temperament Counselor"; (15) "Temperament and School Functioning"; (16) "Temperament and Pediatric Practice"; (17) "Temperament and Nursing Practice"; (18) Temperament and Psychotherapy for Children"; (19) "Temperament and Psychotherapy of Adolescents"; (20) "Temperament and Psychotherapy of Adults"; (21)"Temperament and the Handicapped Child"; (22) "Biological Research on Temperament"; (23) "Temperament and Culture"; (24) "Temperament in Consistency and Change"; and (25) "A Look to the Future." Contains 84 references. (AMC)