PURPOSE: To project the future radiologist workforce through 2055 and assess the contributions of residency positions and attrition to radiologist supply. METHODS: The CMS National Downloadable Files (2014-2023) were used to assess both the current supply of radiologists and model the attrition based on years of practice. Using a nonlinear regression model, differences in attrition patterns were assessed by gender as well as pre-COVID-19 and post-COVID-19. New entrants to the workforce were modeled via linear regression based on National Residency Matching Program data (2005-2024) for radiology residency positions and filled positions. Attrition and new entrants were combined to generate estimates of radiologist supply through 2055. RESULTS: In 2023, 37,482 radiologists were enrolled to provide care to Medicare patients. If residency positions do not grow after 2024, the projected number of radiologists in 2055 is 47,119 or 25.7% higher than in 2023. If residency positions grow after 2024, these projections are 52,591 radiologists in 2055, 40.3% higher. Based on 2014 to 2023 attrition, average years of practice is 35.7 for male and 34.2 for female radiologists. Attrition rates were substantially higher post-COVID-19 versus pre-COVID-19, which difference is equivalent to 3,116 radiologists in 2055. CONCLUSIONS: This study projected that the 2055 radiologist workforce will be 40.3% or 25.7% larger than in 2023 if residency positions, respectively, do or do not grow in the future. The study found that should attrition rates continue to be higher as they have been thus far post-COVID-19, the 2055 radiologist workforce would be substantially smaller.