This article investigated individual control of spacing strategies during study. Three predictions were outlined: The spacing hypothesis suggests that people choose to space their study to improve long-term learning via the spacing effect. The massing hypothesis suggests that people choose to mass their study because of illusions of confidence during study. The metacognitive hypothesis suggests that people control their spacing schedules as a function of their metacognitive judgments of specific to-be-learned items. To test these hypotheses, the authors asked participants to study and make judgments of learning for cue-target pairs. Then, participants were given three choices; they could study the pair again immediately (massed), study the pair again after the entire list had been presented (spaced), or choose not to restudy (done). Results supported a metacognitively controlled spacing strategy-people spaced items that were judged to be relatively easy but massed items that were judged as relatively difficult.