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.