The effect of cations Fe2+ and Fe3+ on the decomposition of apple pectin by the enzymic preparations of Asp. niger and Asp. awamori has been examined. Fe ions have delayed the process of enzymic decomposition of the pectin molecule. In the presence of Fe3+ far less amounts of monogalacturonic acid are formed. The presence of Fe ions makes the pectin molecule more stable to the effect of pectolytic enzymes.