The Strange Situation procedure was developed by Ainsworth two decades agoas a means of assessing the security of infant-parent attachment. Users of the procedureclaim that it provides a way of determining whether the infant has developed species-appropriate adaptive behavior as a result of rearing in an evolutionary appropriate context, characterized by a sensitively responsive parent. Only when the parent behaves in the sensitive, species-appropriate fashion is the baby said to behave in the adaptive or secure fashion. Furthermore, when infants are observed repeatedly in the Strange Situation,the pattern of behavior is said to be highly similar, and this pattern is said to predict the infants' future behavior in a diverse array of contexts. After an exhaustive review of the literature, it is shown that these popular claims are empirically unsupported in their strong form, and that the interpretations in terms of biological adaptationare misguided. There is little reliable evidence about the specific dimensions of parental behavior that affect Strange Situation behavior, although there does appear to be some relationship between these constructs. Temporal stability in security of attachment ishigh only when there is stability in family and caretaking circumstances. Likewise, patterns of Strange Situation behavior only have substantial predictive validity in similarly stable families. Implications for future research and theorizing — particularly as they relate to the use of evolutionary biology in psychological theory — are discussed.