The purpose of this study was to identify the effect of the inquiry and discussion teaching methods compared with the traditional teaching method on the immediate and delayed achievement in Islamic Education for the first secondary Students in one of the Muscat Directorate's secondary schools . More specifically the study attempted to answer the following questions : 1-Are there any statistically significant differences in the immediate achievement in Islamic Education between the first secondary students who are taught by the inquiry and discussion teaching methods and those who are taught by the traditional teaching method ? 2-Are there any statistically significant differences in the delayed achievement in Islamic Education between the first secondary students who are taught by the inquiry and discussion teaching methods and those who are taught by the traditional teaching method ? The experiment was undertaken in the first semester of the 1994 1995 academic year on three first secondary groups at Al-khodh Boys Secondary School, Muscat . The number of the students in the three groups was (88) male students. The procedures of the study included : 1-Content analysis of the Aqidah unit in part I of the first secondary Islamic Education text-book which was validated by specialists in curriculum and methods of teaching Islamic Education who approved its results . The reliability of the content analysis was established by calculating the coefficient of concordance between the analysis done by the researcher that of another researcher (R=0.90). 2-Preparing the lesson plans of the Aqidah unit in accordance with the inquiry and discussion teaching methods. 3-Preparing a (30) item multiple-choice achievement test . Its validity was established by a panel of judges whereas its reliability was established in two ways: the internal consistency (cronbach's alpha = 0.78), and the test-retest method (R=0.75). The test was administered to the subjects twice, the first was to measure immediate achievement and the second to measure delayed achievement. The one way analysis of variance was used for statistical analysis of the data . The most important results were as follows: 1-There were statistically significant differences at the .05 level of significance between the immediate and delayed performance for the students who were taught by the inquiry teaching method and that of the students who were taught by the traditional method. The first group did better than the second . 2-There were no statistically significant differences at the .05 level of significance between the performance of the studens who were taught by the discussion teaching method and that of the students who were taught by the traditional method on immediate and dalayed achievement in Islamic Education