Growing demand for science teachers in the Kingdom of Saudi Arabia, fed by increasing numbers of public school students, is forcing the Saudi government to attract, recruit and retain well-qualified science teachers. Beginning science teachers enter the educational profession with a massive fullfilment and satisfaction in their roles and positions as teachers to educating children in a science classroom. Nevertheless, teachers, over their early years of practice, encounter numerous challenges to provide the most effective science instruction. Therefore, the current study was aimed to identify academic and behavioral classroom challenges faced by science teachers in their first three years of teaching in the Kingdom of Saudi Arabia. In addition, new science teacher gender, school level and years of teaching experience differences in perceptions of the challenges that they encountered at work were analyzed. The present study also investigated various types of support that new science teachers may need to overcome academic and behavioral classroom challenges. In order to gain insights about ways to adequately support novice science teachers, it was important to examine new science teachers' beliefs, ideas and perceptions about effective science teaching. Three survey questionnaires were developed and distributed to teachers of both sexes who have been teaching science subjects, for less than three years, to elementary, middle and high school students in Al Jouf public schools. A total of 49 novice science teachers responded to the survey and 9 of them agreed to participate voluntarily in a face-to-face interview. Different statistical procedures and multiple qualitative methodologies were used to analyze the collected data. Findings suggested that the top three academic challenges faced by new science teachers were: poor quality of teacher preparation programs, absence of appropriate school equipment and facilities and lack of classroom materials and instructional supplies. Moreover, excessive student absenteeism, student readiness to learn science and student lack of interest in science were the three most behavioral challenges encountered by beginning science teachers in the Kingdom of Saudi Arabia. Results also indicated that the perceptions of academic and behavioral classroom challenges may vary according to new science teacher gender, school level and years of teaching experience. More importantly, to become more effective science teachers, novice science teachers are expecting to receive more and better support from their schools. School principals and administrators should provide opportunities for beginning science teachers to attend effective new teacher orientation programs, use complete and well-developed curriculum materials with detailed sequence of teaching procedures, help in dealing with classroom management, and opportunities to participate in successful mentoring programs, coherent in-service training programs and regular professional development programs. Implications for Saudi Arabia government and policy makers, school principals and administrators, students and their parents were discussed and recommendations were made. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]