This article deals with estimating efficiency of world health systems using panel data on World Health Organization (WHO) member countries. The Stochastic Frontier (SF) approach is used for this purpose. We evaluate absolute efficiency as well as rankings and their sensitivity across alternative model specifications using both output-maximizing and cost-minimizing frameworks. We also compare productivity of health service (among countries) derived from the output-maximizing and cost-minimizing models. Results show that efficiency rankings of countries vary substantially depending on whether the goal of healthcare provision is output maximization or health cost minimization. The same applies to different SF model specifications.