This paper presents a new spatial interaction modelling framework for estimating subnational, international migration flows within Europe. We introduce a several-stage model which incorporates constraints at two geographical levels and produces estimates for a full matrices of interregional flows which adhere to known flows between countries in the EU system between 2002 and 2007. It is shown that internal migration data can be usefully employed to help distribute flows subnationally both through in-migration and out-migration distributions and through calibrated distance-decay parameters. Validation of the model outputs is achieved, in part, through comparison with national insurance number registration data from the UK. Keywords: modelling, spatial interaction, migration, Europe, regional