The Articles and Annexes contained within this document constitute the most fine-grained description of the methods and approaches devised in the course of a large collaborative exercise since the 1980s to make estimates of the epidemiology and associated health burden of congenital disorders. The work began at a scientific meeting at WHO Headquarters in Geneva, and has continued in various forms ever since, with input from more individuals than it is possible to acknowledge via the conventional methods of shared authorship. This document is a work in progress, and so its various portions are under development, in the course of which they have been shared with members of the international collaborative group. As the component texts reach the requisite level of maturity, will be added to this document to enable wider consultation with the global community of interested parties. Earlier access to some or all of the texts may be possible – contact b.modell@ucl.ac.uk and m.darlison@ucl.ac.uk to discuss this.