Health care industry is rapidly growing sector in most countries in the world. Hospitals strive to find efficient approaches to improve their service operations. Lean management has been widely recognized from manufacturing and service organizations as managerial philosophy to reduce wastes and increase values to customers. Recently, lean management was adopted in many health care organizations. To promote the success of lean implementation, it is crucial to understand the extent to which lean practices are implemented and their impacts in organizations. Thus, the purpose of this paper is to review lean management, lean practices, and their impact with respect to health care service system context. After reviewing literature, lean practices in health care, important service operations, were determined. In addition, this paper identifies five dimensions of operational performance in health care service organization. These five dimensions are speed, cost, productivity, quality, and customer satisfactions. For the next step of this research project, an empirical study investigating the relationship between lean practices and their impact on operational performance will be carried out.