The problem of the stability of perchlorate ions in the presence of iron group metals is discussed in the light of new experimental results obtained at various temperatures, perchlorate concentrations and pH values. Results obtained with Fe, Co and Ni were compared. It was found that the behavior of nickel in perchlorate solution significantly differs from that of Fe and Co, which have very similar and significant reactivity in the reaction with perchlorate ions. Although the reaction rate with nickel is slow, its role cannot be neglected. The reduction of ClO4- ions in contact with iron group metals, first of all with Fe and Co, is so pronounced that it seems inevitable to revise many statements in text-books and monographs dealing with systems containing iron group metal and perchlorates. It is suggested that electrochemists should consider the reduction process as important evidence that should be taken into account. This also involves that all experimental results and their mechanistic interpretation concerning this field should be revisited. (C) 2005 Elsevier B.V. All rights reserved.