This study aims at knowing the effectiveness of using computer assisted instruction on the achievement of the tenth geography class female students. In order to answer the study questions, the researcher prepared achievement test for the cognitive content of the second unit of 10th class geography textbook/ The validity of this test was conducted by presenting it to (13) referees. Its reliability was also verified by applying it to an external study sample of (30) female students; Cronbach's alpha was found at (0.89). A computerized instructional software was designed. It was validated and evaluated by (17) specialists, and experimented on an external study sample of (30) students. Some modifications were then made to the software. In addition, Raven's progressive matrix was used. The study tools were applied to a sample of (70) 10th class female students at Muscat schools. Those were equally divided into two groups: an experimental with (35) students, and a control with (35) students. The study main conclusions were as follows: -Statistical differences were found at (a= 0.05) between the means of both groups' students in terms of the achievement test; in favour of the experiment group, attributed to the teaching methods. -No statistical differences were found at (a=0.05) between the teaching methods (using Computer) and intelligence level (high/low) The study recommended the need to organize the geography topics of the social studies curriculum to adapt to the nature of its content and to make use of computer software.