The purpose of this study was to determine whether hypermnesia (improved net recall over time) can be differentially affected by manipulating the nature of tasks performed during the intervals between successive recall trials. In Experiment 1, all subjects were asked to imaginally encode separate words and were tested three times for recall. The control group (no interpolated task) produced the hypermnesia effect. Both groups performing interpolated tasks showed sig· nificantly lower recall. A second experiment was conducted in order to replicate these results and to examine the effects of intertest rehearsal on hypermnesia. In Experiment 2, subjects were asked to encode pairs of words using interactive·imagery instructions. Six different interpolated task conditions were employed, varying in the degree to which subsystems of working memory were used. Groups performing imaginal interpolated tasks showed no hypermnesia, whereas those performing nonimaginal tasks did. These findings suggest that access to working memory (see Baddeley, 1986) is not necessary for hypermnesia.Ballard, in 1913, reported an effect in which the net recall of poetry seemed to increase over time, despite the fact that no subsequent learning or rehearsal trials had been given during the retention interval. He described this phenomenon as reminiscence. Subsequent attempts at replicating Ballard's fmdings provided only mixed results (e.g., Buxton, 1943), and investigations of the effect ceased for several years. Buxton's (1943) criticisms of the research procedures used by various experimenters centered around the idea that subjects might be engaging in covert rehearsal or review during the retention intervals and that this might account for the varied results in reminiscence research. He suggested that control of rehearsal during the retention interval might be accomplished either by occupying subject'S minds during retention with such tasks as prose reading, problem solving, and so forth, or by having subjects recall the items in repeated recall trials, thereby ensuring rehearsal during the retention interval.The past decade has brought an accumulation of evidence that must be taken as indicating a strongly renewed