Intrusions and perseverations, although often associated with psychiatric disorders, have a functional role within the information processing system (Eberly, Harkness, & Engdhal, 1991). Research suggests that these phenomena act as conscious aide memoires (Kvavilashvili, 1987) informing the cognitive system that there are prospective tasks to be done (i.e. tasks started, or intentions made, but not finished). In the case of psychiatric problems, the intrusions and perseverations may reflect the presence of unresolved issues that require further processing. The current paper outlines this hypothesis and presents the Zeigarnik effect (Zeigarnik, 1927) as one potential factor amongst others helping to maintain the incidence of intrusions. The paper also describes the possible modus operandi of this effect in terms of post-traumatic stress, obsessive-compulsive disorder and general-anxiety disorder. A number of treatment strategies are discussed which may decrease the incidence of Zeigarnik intrusions.