This report is a long version of the one that was submitted by the “Commission Expert Group1 on the interim evaluation of Gender equality as a crosscutting issue in Horizon 2020” to contribute to the overall interim evaluation of Horizon 2020 as set in Article 32 of the Horizon 2020 Framework Regulation. This report aims to identify possible improvements in the implementation of gender equality (GE) as a crosscutting issue in Horizon 2020. It assists the European Commission (EC) in assessing gender equality, and – in particular – the gender dimension in research and innovation (R&I) content, as a crosscutting issue at the various stages of the implementation of Horizon 2020 from the Work Programme (WP) definition to the funded projects. It aims to provide a solid evidence base for designing future activities and initiatives, in particular the preparation of the exante impact assessment of the next Framework Programme (FP) for Research and Innovation.