Objectives: In response to the gap in the dental literature, the present study aimed at developing a high-quality test to assess clinical reasoning skills in dental students. In addition, it also aimed at understanding the effect of many factors on the level of clinical reasoning development. Methods: An online test was created to assess different skills involved in the process of clinical reasoning using a combination of well-known tools. The innovative approach for this quantitative cross-sectional study was used to assess clinical reasoning in final year dental students from three different schools in the United Kingdom and Saudi Arabia. Response rates were different for each school being 50%, 51% and 45%. The study took place in 2013. Results: The developed tool was valid, reliable and effectively matched to the sample ability. No statistical difference was found between the samples with regards to their gender or curricula. Conclusion: Mixing more than one type of clinical reasoning assessment proved to enhance the effectiveness of assessment. Curriculum effect on clinical reasoning skills found to be minimal for students later in their undergraduate years. Students’ gender has minimal effect on clinical reasoning skills. More research is recommended to further understand the development of clinical reasoning process in dental students.