Background: It is difficult to provide health care services to all those in need of such services due to limited resources and unlimited demands. Thus, priority setting and RATIONING have to be applied. This study aimed at critically examining the concept of RATIONING in health sector and identifying its purposes, influencing factors, mechanisms, and outcomes. Methods: The critical interpretive synthesis methodology was used in this study. PubMed, Cochrane, and Proquest databases were searched using the related key words to find related documents published between 1970 and 2015. In total, 161 published reports were reviewed and included in the study. Thematic content analysis was applied for data analysis. Results: Health services RATIONING means restricting the access of some people to useful or potentially useful health services due to budgetary limitation. The inherent features of the health market and health services, limited resources, and unlimited needs necessitate health services RATIONING. RATIONING can be applied in 4 levels: health care policy-makers, health care managers, health care providers, and patients. Health care RATIONING can be accomplished through fixed budget, benefit package, payment mechanisms, queuing, copayments, and deductibles. Conclusion: This paper enriched our understanding of health services RATIONING and its mechanisms at various levels and contributed to the literature by broadly conceptualizing health services RATIONING.