The Education Endowment Foundation (EEF)'s mission is to break the link between family income and educational achievement. This is achieved through summarising the best available evidence in plain language, generating new evidence of 'what works' to improve teaching and learning, and supporting teachers and school leaders to use research evidence to maximise the benefit for young people. Evidence of what works to raise attainment is primarily generated through randomised controlled trials commissioned by the EEF. These trials include a quantitative impact evaluation to estimate the effect on pupils' attainment (and, in some cases, other outcomes) and an implementation and process evaluation (IPE). This report presents an IPE quality measure and pilots it using data coded in the Review of EEF Projects (Demack et al., 2021) from the 79 EEF trial reports that incorporated IPEs and had been published up to January 2019. [For "Review of EEF Projects. Evaluation Report," see ED625480. For "Review: Scale-Up of EEF Efficacy Trials to Effectiveness Trials," see ED625479.]