In May 2018, the "EUnetHTA Companion Guide” has been launched. The Companion Guide provides central access to all components of the newly established quality management system (QMS) for EUnetHTA (European network for Health Technology Assessment) via a web-based wiki-platform. The purpose of the Companion Guide is to ensure the production of high-quality HTA reports by providing ultimate support and guidance to the EUnetHTA assessment teams during their joint work. The Companion Guide is divided into four main parts: 1. EUnetHTA’s quality management (QM) concept, 2. QM for rapid Relative Effectiveness Assessment (REA) Pharma, 3. QM for rapid REA other technologies (OT) and 4. QMS-related training material. The QM concept paper establishes the main terms and definitions for a common QM understanding amongst EUnetHTA partners and introduces the QMS of EUnetHTA. The assessment processes for rapid REA Pharma and OT have been subdivided into single process steps for which the Companion Guide provides standard operating procedures (SOPs), checklists, templates, guidelines and tools. The user can choose to either see the whole list of SOPs or the SOPs sorted by role in the assessment team (author, co-author, dedicated reviewer). The user will have access to training modules via the Companion Guide which provide information on how to use the Companion Guide. Moreover, the training material enables HTA-doers of all EUnetHTA partners to build up necessary QM capabilities. The content of the Companion Guide is repeatedly subject to evaluation with regard to the achievement of its purpose to ensure high-quality HTA reports.