Abstract: ［Purpose/Significance］This study investigates the research topics of LIS doctors in North America from the 1960s so as to reflect the research topics' evolution and development in the field of library and information science.［Design/Methodology］This study analyzes LIS Doctoral dissertation topics and their publication topics during the period of their doctoral studies so as to reveal the interdisciplinary evolution of LIS doctoral researches in North America since the 1960s. ［Findings/Conclusion］Our results provide evidence that LIS is an interdisciplinary field, and its primary research fields have changed during the past 20 years. They also suggest that advisors’ disciplinary backgrounds have influence on the interdisciplinarity of doctoral dissertations, which exert positive effects on LIS Doctoral research productivity, but few effects on the impact of their papers. ［Originality/Value］With the use of subject categories in ProQuest, the overall data instead of the sample data has been analyzed to explore the scientific research evolution of LIS. Moreover, the influence of tutors’ disciplinary backgrounds on doctoral dissertations and scientific research publications is a new discovery.

Key words: Library and information science, Scientific research topic, Interdisciplinary, Advisors’ disciplinary background, Doctoral education