Cost variation is one of the most concerns of the stakeholders in the construction projects, because it always presents in every construction projects, especially in Vietnam. However, the factors that make the project cost variation are not easy to identify. This study aimed to identify the key factors that influence to the project cost variation. A survey questionnaire was used to collect data from construction practitioners. The analysis results show that there are five groups of factors that

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... influence to project cost variation: Government policies, nature, resources, fraud and theft, and ability of stakeholders. Recommendations are also mentioned to deal with the project cost variation.