The use of computers in education is revolutionizing both learning processes and instructional technology. Computers allow the development of interactive and individualized relations among the learners. The interactive computer based instruction influences the human thought in many ways. Children learn differently with computers when compared to the traditional teacher based instruction. Computers motivate children to learn collaboratively rather than to complete with other children. Computer as an educational tool is used to enhance learner's skill in academic subjects at all levels of education. Researchers have made it clear that computer assisted instruction is effective in many learning situations. An assessment of the effects of computers on learning is a complicated process since it involves human computer interaction. In this context, an attempt is made to find out the impact of different instructional strategies viz. Lecture Method (LM), Computer Assisted lnstruction as individualized instructional strategy (CAI) and Computer Assisted Instruction with Peer lnteraction (CAIPI) on the achievement of students in physics. It is found that CAlPl is the most effective instructional strategy in enhancing the achievement of students in physics. Further, it is obsetved that CAlPl is also effective in enhancing the retention of the learners in Physics. The results are discussed in this study.