Quantitative analysis by electron probe micro analysis (EPMA) is usually carried out by reference to materials of known composition (standards) but because of the low X-ray yield arising from electron bombardment of low atomic number elements there is a particular problem when analysing these elements. This paper addresses the problem by describing briefly the production and certification of reference materials for two elements, carbon and nitrogen. Cementite (Fe3C), a line compound, was chosen as a suitable material for carbon and γ′-Fe4N for nitrogen. The compounds were produced by, respectively, carburising or nitriding pure iron under carefully controlled conditions. Particular emphasis is placed on a homogeneity study, background correction methods and methodology validation using these reference materials. A linear relationship was established between the certified content of the material and zero. Certified values (6.69±k 0.13 wt% C and 5.77±k 0.094 wt% N) were assigned for the composition, where k is the coverage factor.