A new method for estimating catalytic effects in differential pulse polarography and differential pulse voltammetry is proposed. Based on an approximate equation relating the catalytic peak current with that of the uncatalysed reduction of metal ions, the new method is applicable when the ligand concentration is much smaller than the analytical concentration of the metal ion. The method has been tested with previously studied Ni(II)-(native or denatured) DNA electrocatalytic systems. Its main advantage appears when the electrocatalytic peaks are poorly resolved.