Previous research has demonstrated the importance of examining the instructional efficiency of academic interventions and has defined efficiency as the number of items learned per instructional minute. Maintenance of the skill is also an important instructional goal, however. Therefore, the current study compared efficiency metrics using initial learning and maintenance with 25 fourthgrade students. Each student was taught the pronunciation and English translation of 12 words from the Esperanto international language with two instructional conditions (six words for each condition). The first condition was traditional drill (TD) rehearsal with all unknown words, and the secondwas incremental rehearsal (IR)with one unknown and eight knownwords. Results indicated that, although the IR condition led to significantly more words being retained, TD was significantly more efficient using initial learning. The two conditions were equally efficient, however, when maintenance data were used. Therefore, evaluating the efficiency of instructional interventions should consider maintenance data as well.