RATIONALE AND OBJECTIVES: To determine the frequency and predictors of lack of research output by medical doctors after PhD graduation in radiology. MATERIALS AND METHODS: This study included all 272 PhD theses by medical doctors in the Netherlands between 2000 and 2016, with radiology as the field of research of the primary doctoral supervisor. Post-PhD research output was considered lacking if no original research, systematic review, or meta-analysis was published as first, second, or last author in the post-PhD period. RESULTS: The percentage of PhD graduates without research output was 41.9% (78/186) at 5 years, 28.6% (24/84) at 10 years, and 16.1% (5/31) at 15 years in the post-PhD period. On univariate Cox regression analysis, only female gender emerged as a significant predictor of a lack of research output in the post-PhD period (odds ratio: 1.456, 95% confidence interval: 1.023-2.073, p = 0.038). PhD student's age, being a radiologist or not before PhD graduation, the radiologic subspecialty topic of the PhD thesis, the H-index of the primary doctoral supervisor, the institution at which the PhD was performed, and the number of publications in the PhD period, were not significantly associated with lack of post-PhD research output. CONCLUSION: A considerable proportion of medical doctors has no active research output after obtaining a PhD degree in radiology, and this should be taken into account when relying on PhD programs to replenish the physician-scientist workforce. Females appear to be more prone to lack active research output, and this should be addressed by the scientific community and society.