This study aimed at investigating the effectiveness of applying the concept mapping in teaching Fiqh on the achievement of the second grade Preparatory School students. The study sample was formed of two classes of the second grade students of Hammam bin Hazim Preparatory School - Directorate General, Muscat Governate for the academic year 2003 / 2004. The study sample was divided into two controlled and experimental groups of 30 students cach. To verify the objectives of the study the researcher prepared a pre, immediate and delayed achievement test for the Fiqh unit of the second year Preparatory School and administered it on the study sample. The results revealed the presence of statistical significance differences at (0.05) level between the two controlled and experimental groups in favour of the experimental group in the immediate test. The results also showed statistical significant differences at (0.05) level between the experimental and controlled groups in favour of the former in the immediate test. In the light of the study findings the researcher presented a number of recommendations in the field of Islamic Studies curricula and teaching methods and recommended conducting considerable research in the field of map concepts.