background improving efficiency of health sector is of particular importance in all countries. to reach this end, it is paramount to measure the efficiency. on the other hand, there are many factors that affect the efficiency of health systems. this study aimed to measure the technical efficiency (te) of health systems in economic cooperation organization (eco) countries during 2004–10 and to determine the factors affecting their te. methods this was a descriptive-analytical and panel study. the required data were gathered using library and field studies, available statistics and international websites through completing data collection forms. in this study, the te of health systems in 10 eco countries was measured using their available data and data envelopment analysis (dea) through two approaches. the first approach used gdp per capita, education and smoking as its inputs and life expectancy and infant mortality rates as the outputs. the second approach, also, used the health expenditures per capita, the number of physicians per thousand people, and the number of hospital beds per thousand people as its inputs and life expectancy and under-5 mortality rates as the outputs. then, the factors affecting the te of health systems were determined using the panel data logit model. excel 2010, win4deap 1.1.2 and stata 11.0 were used to analyze the collected data. results according to the first approach, the mean te of health systems was 0.497 and based on the second one it was 0.563. turkey and turkmenistan had, respectively, the highest and lowest mean of efficiency. also, the results of panel data logit model showed that only gdp per capita and health expenditures per capita had significant relationships with the te of health systems. conclusion in order to maximize the te of health systems, health policy-makers should pay special attention to the proper use of healthcare resources according to the people’s needs, the appropriate management of the health system resources, allocating adequate budgets to the health sector, establishing an appropriate referral system to provide better public access to health services according to their income and needs, among many others.