In order to control the quality of element determinations in glass, the Standards, Measurements and Testing Programme (formerly BCR) of the European Commission has starred a project in which the final aim is to certify a glass reference material for its content of a range of trace elements (As, Ba. Cd, Co, Cr. Pbl Sb, Se), fluoride and chloride. The first part of this project consisted in a series of interlaboratory studies which aimed to test the feasibility of preparation of candidate glass reference materials and to detect and remove most of the pitfalls observed in element determinations. This paper presents the main results of the interlaboratory studies carried out prior to the certification campaign of a glass reference material.