The task group report presented in this publication is one of a series prepared by eminent psychologists who have served as consultants in the U.S.O.E.-sponsored grant study to conduct a Critical Appraisal of the Personality-Emotions-Motivation-Domain. In order to achieve the goal of identifying important problems and areas for new research and methodological issues related to them, an approach was followed in which leading investigators in specialized areas were enlisted as members of task groups and asked to reflect on their current knowledge of ongoing research and to identify the research needs in their respective area. The articles in this report are: (1) Interpersonal Behavior Processes: An Overview (Byrne); (2) Courtship, Marriage, and Other Long-Time Interpersonal Relationships (Levinger); (3) Interpersonal Aggression (Baron); (4) Behavioral Aspects of Interpersonal Behavior (Mehrabian); and (5) Environmental Effects on Interpersonal Behavior (Griffith). (Author)