Adult attachment research has proceeded on the assumption that attachment style is relatively stable and affects future functioning. However, researchers have become interested in attachment instability and predictors of attachment style change. In this article, 2 conceptualizations of attachment style change were examined: Attachment style change is a reaction to current circumstances, and attachment style change is an individual difference in susceptibility to change that is associated with stable vulnerability factors. A total of 155 women were assessed after high school graduation, and 6 months and 2 years later. Results primarily supported the conceptualization of attachment style change as an individual difference. Specifically, some women may be prone to attachment fluctuations because of adverse earlier experiences, and women who show attachment fluctuations are similar to women with stably insecure attachments.