Activity of phytate dephosphorylation was determined in 26 samples of cereals, legumes, oilseeds and complete diets for poultry using the colourimetric and isotachophoretic method. The former method was based on the colour formed upon the reaction of molybdate with phosphate released from phytate. The latter method was based on measurement of decrease of phytate concentration in the reaction mixture. Rye had by far the highest phytate dephosphorylation activity, followed by wheat and wheat-containing diets. However, for most of the other samples, this activity was low. Phytate dephosphorylation activity as measured by capillary isotachophoresis was numerically lower than activity measured using the molybdate method; however, activities assayed by both methods correlated with statistical significance (r=0.86; P<0.001). The isotachophoretic method may be suitable for phytate dephosphorylation activity assay in feeds with a high content of inorganic phosphate and in samples of digesta and faeces.