Case tracking (following-up prior patient encounters) can help inform future clinical decisions and supplement experiential learning. Internal medicine subspecialty fellows see a high volume of patients and need to become subject matter experts within a short time frame, yet little is known about their specific needs and motivations around case tracking. The objective of this study was to explore internal medicine subspecialty fellows' motivations, preferences, and practices around case tracking. We conducted interviews with internal medicine subspecialty fellows at a single academic medical center during the 2022-2023 academic year. Interviews were analyzed using qualitative content analysis. 22 fellows were interviewed for our study. We found that most fellows engaged in case tracking with lists in the electronic health record (EHR). Fellows primarily tracked cases of clinical uncertainty and patients with specific diseases or conditions of interest. Fellows sought information on patients' health outcomes, results, and clinical notes. Motivations for tracking were predominantly related to curiosity, professional growth, and development of practice patterns. Barriers to case tracking included time, challenges maintaining patient lists, losing track of patients, and lack of motivation to develop and maintain an organized system. Internal medicine subspecialty fellows engaged in and valued case tracking as a way to supplement their experiential learning. Our study highlighted their current practices, motivations, preferences, and challenges related to case tracking. We plan to use these findings to help develop an EHR-embedded dashboard to facilitate case tracking among subspecialty fellows.