The authors review the theory of romantic, or pair-bond, attachment as it was originally formulated by C. Hazan and P. R. Shaver in 1987 and describe how it has evolved over more than a decade. In addition, they discuss 5 issues related to the theory that need further clarification: (a) the nature of attachment relationships, (b) the evolution and function of attachment in adulthood, (c) models of individual differences in attachment, (d) continuity and change in attachment security, and (e) the integration of attachment, sex, and caregiving. In discussing these issues, they provide leads for future research and outline a more complete theory of romantic attachment.During the past 12 years, attachment theory has become one of the major frameworks for the study of romantic relationships. It has generated hundreds of articles and several books, not to mention countless PhD and MA theses. An increasing number of conference papers and requests for reprints and information suggest that the study of romantic attachment will continue to attract interest for years to come. One reason for the popularity of the theory, we believe, is its provision of a unified framework for explaining the development, maintenance, and dissolution of close relationships while simultaneously offering a perspective on personality development, emotion regulation, and psychopathology. Moreover, the theory is intellectually rich, merging data and insights from disciplines as diverse as ethology, physiological psychology, control systems theory, developmental psychology, cognitive science, and psychoanalysis.