Abstract-Recently, agile software development methods have attracted the attention of academic and industrial domains. Unlike traditional approaches, agile methods focus on rapid delivery of business value to customers through fast delivery of working code. Therefore, requirement prioritization is considered a crucial process in this context, since there is the need to identify which requirements must be developed first, based on stakeholders preferences and taking into account business and technical challenges such as dependencies of tasks, developers skills, limitation of budget, etc. In Scrum, the most popular agile method, requirement management is done by maintaining the product backlog, which contains the list of functionalities that must be developed. Although some works conducted systematic reviews on the topic of agile requirement engineering, to the best of our knowledge, there is no study that reviewed the specific subject of ordering the product backlog in agile projects. Therefore, in this work, we conducted a Systematic Literature Review of studies on this topic published up to (and including) 2016 through a database search, to identify and analyze factors and techniques used to accomplish the task of ordering the product backlog in agile projects. In total, we evaluated 1556 papers, of which 13 reported on the subject of study.