Abstract A method to discriminate between the catalytic, CE, ECE and EC mechanisms is proposed. This method is based on the kinetic effects that are observed on different time scales in normal pulse polarography (NPP) and in dc polarography (DCP). Thus, if we consider the experimental observable, consisting of the ratio of the instantaneous limiting current in NPP over the instantaneous limiting current in DCP, and we plot this observable vs. log χ DCP, the curves obtained are different for each of the mechanisms given above. In these plots χ DCP=( k 1+ k 2) τ, where k 1 and k 2 are the rate constant values of the chemical reaction and τ is the drop time. These plots also allow the values of the rate constants to be found for the catalytic, CE and ECE mechanisms when the diffusion coefficient or the bulk concentration of the species involved in the electrode process are not known.