This report explores ways to better measure learning mobility in vocational education and training (VET). Promoting the mobility of VET students is an important goal of EU policy making in the field of initial vocational education and training, and education in general. The Erasmus+ programme invests heavily in this objective. However, we are missing comparable data across EU countries on VET learning mobility, and this limits the opportunities for monitoring progress made in this field. The report looks into the potential availability of administrative data sources, in particular the data collected as part of the Erasmus+ programme.