This chapter deals with what may be considered as the most intriguing question in relation to involuntary autobiographical memories, namely, how and why they suddenly come to mind. However, some of the challenges associated with this question are not limited to this class of memories. The theoretical problem of how an unconscious state (i.e., an event stored in memory) may at a certain time attain the quality of consciousness, so that we can subjectively relive and re-experience it, of course also pertains to memories that are recalled voluntarily. Voluntary retrieval is often described as a cyclic process, beginning with a search description that specifies the to-be-remembered information in response to a retrieval request (e.g., where did I put my keys?) and gradually narrows in on a set of alternatives, until we think we have found the right answer (Norman and Bobrow, 1979). One puzzle in relation to involuntary memories is how such circling in can take place without an initial search description and without a goal-directed search process.