This chapter examines social and behavioral science theoretical perspectives currently included in the conceptual base of Human Behavior in the Social Environment curricula for their utility in understanding "diverse persons in diverse environments," with special attention to gender. The systems perspective sees human behavior as the outcome of reciprocal interactions of persons operating within organized and integrated social systems. Feminist criticisms have attacked the use of a systems perspective in family therapy, on the grounds that it lacks attention to the social, economic, political, and historical contexts of gender. The conflict perspective has emerged over and over again in history to draw attention to conflict, dominance, and oppression in social life. The psychodynamic perspective is concerned with how internal processes such as needs, drives, and emotions motivate human behavior. The developmental perspective focuses on how human behavior changes and stays the same across the life cycle.