The present study investigated the levels of geometrical thinking within teacherstudents according to Van Hiele theory. It also investigated the difference in their performance on the thinking levels test, the geometrical thinking levels (recognition, analysis, ordering, deduction) and their geometrical achievement. The study aims at answering the following questions: 1- What is the geometrical thinking level achieved by student teachers with reference to Van Hiele theory ? 2- Does performance of student teachers on geometrical thinking test differ according to their thinking level (recognition, analysis, ordering, deduction)? 3- Does performance of student teachers on geometrical thinking test differ according to their achievement level (high, average, low)?. The study sample was composed of 155 students (males and females) from colleges of education and Sultan Qaboos University. Students were enrolled in fourth year course in Mathematics for the academic year 2002/2003. The researcher developed the geometrical thinking test as well as geometry achievement test. The results showed that:- Only 5% of the students did not succeed to be classified under any level of geometrical thinking levels according to Van Hiele, but 65% of the students classified according the expected geometrical thinking levels of Van Hiele theory. - Significant statistical differences between the recognition level and all other levels. - Significant statistical differences between the analytical level and the deductive level in favor of the analytical level. - Non-Significant statistical differences between the ordinal and the deductive level. - Significant statistical differences in student's performance on the geometrical thinking levels test which is referred to the achievement level in geometry. The study stressed the need for a review of the methods of teaching of geometry, considering that such a scientific methods should be taught through problem solving styles with concentration on all stages of concepts development in geometry in order to get the higher levels of geometrical thinking.