This report covers the proceedings and conclusions of a workshop on Interoperability in GI and GIS, held at the Joint Research Centre, Ispra, in February 1999. The workshop focused on four major themes: metadata, modelling, technologies and information communities. The broad range of requirements and recommendations that arose from the discussions immediately suggested a network of groups each focussing on a different aspect of the interoperability issue. The network would contain systems from European (and other global) GIS vendors for the purpose of evaluating emerging GIS technology, particularly with respect to long term interoperability issues including standards development, benchmarking and branding, hence the term Virtual Interoperability Laboratory for Europe.