Research motivation: the research is motivated by the urgent need of electronic medical record (EMR) in developing countries to address major health problems. Theoretical backgrounds: concepts of institutional theories formal rules and informal constraints Research setting: the case of development and implementation of EMR for children in Ho Chi Minh city, Vietnam Research method: qualitative research tradition and comparative case study Analysis and findings: clinics where the system implemented are classified into two groups based on their level of successful implementation, the overlapping between formal rules and informal constraints are analyzed to identify social conditions that contribute to the differences in outcomes. Contributions: the paper contributes a practical guideline in building EMRs in resource constraint settings; it also helps to give better understanding on how the relation between formal rules and informal constraints affects the success or failure of EMRs implementation.