The aim of this study was to determine the acquisition of funda mental concepts in Islamic education textbooks achieved by Preparato ry school students in the Muscat Region . This general aim can be broken into several specific objectives that correspond to the following questions: 1-What are the fundamental Isalamic concepts in Islamic Education textbooks at the preparatory school level ? 2- What is the level of achievement of students in the Muscat Region in their acquisition of the fundamental concepts in Islamic education textbooks used in the preparatory schools ? 3- Are there any significant differences in the level of achievement in these concepts which could be attributed to gender and instructional level ? The population of the study consists of 20258 male and female stu dents of three instructional levels in the Preparatory school level of the government school system run by the Muscat Directorate of Education for the academic year 1993 - 94. The sample consists of 531 male and 481 female students. The Islamic education textbooks in the preparatory school were an alysed and 43 common concepts were identified and classified into five fields : "Aqidah", "Shariah", "Akhlaq", "Sirah" and "Tajwid" . Then an objective multiple choice test was prepared. The validity of the test was determined by a committee of special ists in Islamic education and educational measurement. The test was found to be valid in that it made it possible to detect a significant statis tical difference between the upper 27% and the lower 27% of the sam ple of the study. The reliability of the test was determined by two methods : a- A computation of the coefficient Alpha which is an indicator of the internal consistensy (0.85). b- Test - Retest method , the Pearson correlation coefficient was (0.61) and this value was statistically significant . The test was administered in its final form to the sample of the study in the second semester of the academic year 1993-94 .The results of this study were as follows: 1- The level of achievement of the students at the preparatory school in the acquisition of the fundamental concepts in Islamic education text books was less than satisfactory : with an average of (47.34) for the first graders , (56.20) for the second graders and (60.13) for the third graders 2- There were significant statistical differences between students' grades means in the three calsses , in favor of the higher class in the test as a whole 3- There were no significant statistical differences between male and fe male students in the test as a whole.