This volume examines behavioral genetic research on temperament and personality from a number of perspectives. It takes a developmental perspective on a number of issues across the lifespan, focusing on personality and temperament. The first section focuses on the development of temperament and personality. Typically this has involved exploring genetic and environmental contributions to phenotypic stability and instability, but more recently there has been research that examines the etiology of intra-individual change/growth trajectories. The second section examines genetic and environmental contributions to the association between temperament and personality and other behaviors. The third and fourth sections discuss genotype-environment correlations and interactions, and introduces the reader to molecular genetics research on temperament and personality. Chapter 11 will discuss the significance of this type of research and Chapter 12 will provide an example of specific line of research exploring genes associated with temperament.