This paper identifies and elaborates the unique conditions that differentiate stepfamilies from first families and evaluates and critiques the theory and methods used to study stepfamilies. The paper begins with a summary of past and current demographic trends, followed by a discussion of children and their custodial arrangements, the factor that most profoundly distinguishes a stepfamily from a first family. Next, the difficulties associated with stepmother, stepfather, and stepchild positions are reviewed. Certain processes (e.g. commitment, cohesion, communication) are important for the formation and stable maintenance of all family groups. One of these processes, boundary maintenance, is used to illustrate the unique experiences of stepfamilies. The stepfamily as a high risk setting is next discussed. Suggestions that are offered in the literature to explain stepmember vulnerability to abuse are summarized. The paper concludes with a discussion of theory and methods and the progress, problems, and promising directions of this research topic.