This study aimed at investigating the effect of using MATHEMATICA Program in teaching the " Triple-Integrate " unit and the previous level of achievement ( high , medium , low ) on students achievement in this unit. The study also investigated the effect of interaction between the method of teaching and the previous level of achievement. The sample of the study consisted of (45) ( Math/Computer) students at the College of Education in Sohar. (23) students were assigned randomly to the experimental group and (22) students comprised the control group. The equality of the previous achievement of both groups was assured. The two groups were divided into three levels according to their grades in Calculus(1) which was achieved by students in the first semester (2002/2003)... Two way ANOVA was used as well as scheffe test for postcomparisons. The study results were as follows: 1. There were statistically significant differences (a = 0.05) between the students means of scores in the achievement test due to the method of teaching favoring the students taught by MATHEMATICA. 2. There were statistically significant differences at (a = 0.05) level in the achievement test due to previous achievement in Calculus(1) favoring high achievement students and there were no statistically significant differences at (a = 0.05) between the means of scores of medium achievement and low achievement students. 3. There were no statistically significant differences at (a = 0.05) level due to interaction between the method of teaching and Previous level of achievement in Calculus(1) on achievement in the " Triple- Integrate " unit. In the light of these results, the study recommended the use of MATHEMATICA in teaching the " Triple-Integrate " unit with clear strategies for different levels of achievement in integration boundary.