A study was made to determine how the rate of spelling and the retention of spelling words was influenced by the number and spacing of practice presentations on unlearned words. Sixth-grade students (42) in East Palo Alto were drilled by a computer for 6 weeks on six lists of 12 different spelling words each. They drilled on one list until (1) they spelled 10 of the 12 words correctly, or (2) they had gone through the list once a day for 5 succeeding days. Three experimental treatments were used, differing only in the number and spacing of repetition trials a subject had on those words he missed during a daily session. A third of the words on any subject's list were randomly assigned to one of the following categories: (1) no repetition during a daily session, (2) immediate repetition after a 6-second study interval, and (3) spaced repetition in which words were repeated after four other items had been presented. A retention test over all words was given at the end of the experiment. Of the three approaches, additional practice was more effective than no repetition, and spaced-repetition was consistently favored over the other two. Contrary to earlier research, the findings of this study indicated that immediate repetition, as well as spaced repetition, did produce substantial learning. (Author/LH)