For the purpose of controlling the quality of element determinations in glass, the Standards, Measurements and Testing Programme (formely BCR) of the European Commission has produced a glass reference material which was certified for its content of a range of trace elements (As, Ba, Cd, Co, Cr, Ph, Sb, Se) and chloride. This certification followed a series of interlaboratory studies which enabled us to detect and remove most of the pitfalls observed in element determinations. This paper describes the preparation of the glass reference material CRM 664, the homogeneity study and the analytical work performed for the certification.