Incremental rehearsal (IR) is a highly effective intervention that uses high repetition and a high ratio of known to unknown items with linearly spaced known items between the new items. It has been hypothesized that narrowly spaced practice would result in quick learning, whereas items that are widely spaced would result in longer-term retention. The current study examined the effect of spacing by teaching vocabulary words to 36 fourth-grade students. Each student was randomly assigned to a widely spaced IR condition (i.e., one unknown item, one known item, one unknown item, two known items, one unknown item, three known items, and an increase in the number of known items presented each time by one) or an IR condition in which spacing increased exponentially (IR-Exp; i.e., one unknown item, one known item, one unknown item, two known items, one unknown item, four known items, and one unknown item, eight known items). The results indicated that the students in the study retained twice as much information with the widely spaced IR than with the IR-Exp condition, but the latter required half as much time. IR and IR-Exp were equally efficient, but IR continues to be superior to all other flashcard approaches in improving retention.