One of the most notable findings in contemporary behavior genetics is that children growing up in the same family are not very similar. The nine chapters in this book examine the contribution of genetics, shared environment, and nonshared environment to development. Chapters include: (1) "Behavioral Genetic Evidence for the Importance of Nonshared Environment" (Robert Plomin and others); (2) "Estimating Nonshared Environment Using Sibling Discrepancy Scores" (Michael J. Rovine); (3) "The Separate Worlds of Teenage Siblings: An Introduction to the Study of the Nonshared Environment and Adolescent Development" (David Reiss and others); (4) "Young Children's Nonshared Experiences: A Summary of Studies in Cambridge and Colorado" (Judy Dunn and Shirley McGuire); (5) "Sibling Relationships and Their Association with Parental Differential Treatment" (Gene Brody and Zolinda Stoneman); (6) "A Comparison of Across-Family and Within-Family Parenting Predictors of Adolescent Psychotherapy and Suicidal Ideation" (Maria Tejerina-Allen and others); (7) "Peers and Friends as Nonshared Environmental Influences" (David C. Rowe and others); (8) "Nonshared Environments and Heart Disease Risk: Concepts and Data for a Model of Coronary-Prone Behavior" (Craig K. Ewart); and (9) "Sibling Similarity as an Individual Differences Variable: Within-Family Measures of Shared Environment" (James E. Deal and others). Each chapter contains a list of references. (MDM)