The instrumental neutron activation analysis technique (INAA) was used for homogeneity tests and certification analyses of coal fly ash reference materials ENO, ECH, and EOP prepared at the Institute of Radioecology and Nuclear Techniques (IRANT), Koice, Czechoslovakia. Quantitative estimation of a degree of inhomogeneity was suggested. The relative standard deviations due to inhomogeneity were found to be <1% for macroconstituents and <3% for minor and trace elements for sample weights about 25 mg. The results of determination of the elements Al, As, Ba, Ca, Ce, Co, Cr, Cs, Dy, Eu, Fe, Ga, Hf, In, K, La, Mn, Na, Nd, Ni, Rb, Sb, Sc, Sm, Sr, Ta, Th, Ti, U, V, W, and Zn were compared with the IRANT certified or information values. NBS SRM 1633a Trace Elements in Coal Fly Ash was also analyzed as a control sample and the results for the above elements were compared with the NBS certified, information or literature available values. From these comparisons, inference was made on the quality of the IRANT specified values for the element contents.