Academic and professional literature records the primary areas of interest within a discipline and how they change across time. However, it does not always keep up to date with the practical needs of various industries. This article discusses the Project Management Body of Knowledge (PMBOK) areas and their implementation among active project managers (PMs). The PMBOK guide defines terms, guidelines, and knowledge areas within project management. A survey was conducted among 117 active PMs who were asked to rate the degree to which they implement the PMBOK areas. PMs reported integration, cost, and procurement as being implemented by them to the greatest extent, while their implementation of quality, scope, and stakeholders was not reported. This points out the need for reinforcement among PMs. No correlation was found between the degree to which additional knowledge was implemented by PMs and the degree to which the knowledge areas were covered in the last generation of textbooks. Textbooks do not align with the PMs’ implementation in their working fields. The study identified gaps between the degree to which the knowledge areas of project management were implemented and the importance that the authors of the textbooks attach to the above areas of knowledge. The research findings may contribute greatly to reducing these gaps. They can also contribute to training programs targeted at project managers.