Attachment theory, currently a dominant theme in the study of early social development, is beginning to have a presence in clinical psychology as well. A review of the theory as proposed by Bowlby is followed by an examination of the related research literature. Research using Ainsworth's Strange Situation paradigm suggests that the infant's attachment status is a genuine product of the interaction between mother and child rather than a measure of infant temperament, and is related to a broad array of developmental variables. Relatively little research has effectively examined the link between the mother-infant relationship and adult social functioning, however, due in part to difficulties with the measurement of attachment-related constructs. It is concluded that while the theory continues to evolve and some critical issues remain unresolved, attachment may be a useful construct for conceptualizing many disorders, and has the potential to provide valuable insights regarding the process and techniques of psychotherapy.