Abstract: A dry analytical element for use in the measurement of activity of enzyme in an aqueous liquid, such as, body fluid, having one or more water-retaining layers. The enzyme has an optimum pH in a in pH range within which the dissociation of p-nitrophenol is insufficient for color formation. The layers of the element comprise a self-developing substrate having p-nitrophenol group attached to the molecular structure through an ether or ester linkage and a cationic polymer, said self-developing substrate and said cationic polymer being incorporated separately in different water-retaining carriers which are arranged to allow the layers to have liquid contact with each other.