The general theory of d.c. relaxation techniques has been developed mainly for single-step electrochemical reactions and for multi-step reactions with a clearly defined rate-determining step and no intermediate accumulation either on the electrode surface or in the solution. A few workers have considered the case of multi-step reactions, but, because of the complexity of these systems, different approximations and simplifications were introduced in every treatment, limiting the general usefulness of the conclusions. Using numerical calculational methods, we have investigated the behavior of two-step (metal deposition/dissolution) reactions for potentiostatic and galvanostatic single- and double-pulse relaxation experiments. We have carried out a large number of numerical simulations using a wide range of variable values. The main purpose was to determine the conditions under which the techniques are applicable for the measurement of the rate constant of the fast and the slow step of the reaction sequence. In particular, two ’critical times’ were determined : (i) the time to reach ’steady-state’ conditions with the transient techniques and (ii) the time available for the determination of the fast-step kinetics at the beginning of the measuring pulse. We have succeeded in representing these conditions in graphical form as a function of parameters involving only a few (mostly known) variables. We also found that the appearance of a maximum/minimum in the relaxation curves indicates that only the fast-step kinetics can be determined.