External quality assessment (EQA) is an important component of quality systems for blood transfusion services. Establishing external quality assessment programmes for screening of donated blood for transfusion-transmissible infections (TTI): implementation guide aims to support WHO member States in establishing and operating EQA programmes for screening donated blood for TTI. The guides has been designed for use by national health authorities and EQA organizing institutions in the development of EQA programme. It will also give participating laboratories an insight into the organization of EQA programmes for TTI screening and an understanding of the benefits of participation.