The purpose of this study is to examine the process through which medical students develop the professional expertise required to be a doctor. To achieve this end, various factors affecting specialization were broadly analyzed to develop diagnostic measures to examine the process of professional socialization. These measures consist of 24 analytic factors, 13 being profession-specific, 6 concerning self-management and 5 related to sociability with others. In all they prove to be highly reliable diagnostic measures. The confidence level of profession-specific factors is measured at 0.909 while those of self-management factors and sociability with others are computed at 0.725 and 0.830 respectively. The results from examining the process of professional socialization of medical students indicate that the respective year of medical study affects the profession-specific factors the most. It was also found that life satisfaction level as a medical student exerted the greatest influence on self-management factors. As for sociability factors, the year in medical school was notably the most significant variable. The more senior the students were, the more likely they displayed leadership. More junior students, on the other hand, showed qualities of compassion, peer support and willingness to serve others. We expect that the findings of our study will help identify pressing issues and needs in facilitating specialization of medical students. In turn, it is hoped that a curriculum can be developed through which students are able to find their special skills at an opportune moment.