|The purpose of this paper is to develop a CAI program and apply it to the students to see its effectiveness for middle school students in understand how unconformity is formed. This CAI program was developed with 16 bit IBM-pc compatible computer using ``KAS (Korea Authoring System) Ver. 2.2. This program consists of 125 pictures and can be used for 45 minute instruction period. The number of KAS lines in this program is about 1300. This program was made to enhance students` achievement on the concept of geological unconformity through animation and sound effects. This research is considered to have the interaction effect between the computer and learner, and material was made to assess the results of the learning. The results of its application revealed that the control group (38 students) was more excellent in their achievement than those (37 students) who didn`t use this program. The achievement rate of the control group was 56.84% whereas that of the other group was 49.46%. This result shows that this CAI program is very effective.