In order to better support Member States in achieving the Sustainable Development Goals (SDGs), the United Nations Economic Commission for Europe (UNECE) identified four areas where its programmes and expertise converge. These "nexus" areas are sustainable use of natural resources; sustainable and smart cities for all ages; sustainable mobility and smart connectivity; and measuring and monitoring progress towards the SDGs. This publication supports efforts within the fourth nexus area, measuring and monitoring progress towards the SDGs. The focus is on the challenges faced by countries in the UNECE region.