Three calculator tests were administered to a national sample of 1,469 Irish students in Grade 9--the last cohort to study mathematics without calculators (Phase 1). Three years later, the same tests were administered to a similar sample with calculators (Phase 2). Scores on a test of calculator-inappropriate items showed no significant change over the 3 years. For a test of calculator optional items, students were divided randomly into 2 groups, 1 with calculator access and the other without. In both phases, the students with calculators achieved significantly better than the students without calculators. Achievement on a test of calculator appropriate items showed significant improvement over the 3 years. Students' attitudes toward calculators also improved over the time. (Contains 6 notes, 11 tables, and 2 figures.)