The problem of the reduction of perchlorate ions is discussed in the light of recent results bearing in mind the perchlorate environmental contamination challenge and recent problems concerning the electrochemical stability of ClO4- ions. The catalytic and electrocatalytic transformations are compared in the case of WC and Pt electrodes (catalysts). Various methods for the detection of the occurrence of the reduction process are presented (radiotracer technique, potential step method and voltammetry). It is shown that the interpretation of the results of studies of corrosion processes of Al, Zn, Cu, Ni and Fe carried out in the presence of ClO4- ions cannot be considered as adequate without taking into consideration the reduction of ClO4- ions and all previous work should be revisited on the basis of the new findings. Some elements of the mechanistic aspects of the complicated reduction processes are discussed. (C) 2003 Elsevier Science B.V. All rights reserved.