Background: Approximately 20 years after the launch of managed care (MC) in Germany, the initial dynamics have turned into an MC backlash with a poor image for MC among physicians and the insured. Factors in MC contract rejection by physicians have not previously been studied systematically. Objective: The objective of the study is to show that observed physician characteristics explain MC contract rejection in a quantitative model. These econometric findings will be related to suitable political measures to foster physicians' MC acceptance. Methods: Results are based on 500 completed responses to a survey among practicing physicians in Northern Germany. Physician cooperation, attitudes toward MC, and practice characteristics are addressed. A Heckman approach accounts for potential preselection of physicians by insurers. Econometric findings are complemented by a qualitative analysis of free-text answers. Results: Private patient share, physician age, and number of physicians per practice significantly increase rejection probability, whereas it is decreased by rural location. Qualitatively, administrative burden and loss of professional autonomy are the main reasons for MC refusal. Conclusion: Current health policy focuses on institutional measures such as innovation funding to promote MC. Our results show that it may be more effective to turn attention to practicing physicians' preferences as a bottleneck to MC development.