Problems concerning transients in the non-linear j/eta region are discussed. Numerical equations and a program for personal computers to calculate galvanostatic and modified coulostatic transients in the non-linear region enabled (i) calculation of transients obtained with single and twin working electrode cells, (ii) estimation of the span of overpotential (as a function of the kinetic and experimental parameters of the system) to record transients in the linear region, (iii) choice of cell configuration (single or twin working electrode), (iv) calculation of correction factors for errors in j(O) and C-dl, resulting from treatment of transients which moderately exceed the linear region using curve fitting to analytical equations which are restricted to the linear region, (v) curve fitting on a PC using numerical expressions. The exchange current densities of the Cd2+Cd(Hg) system were studied using the modified coulostatic method in the linear and non-linear region. The linear region could be studied only with a twin working electrode configuration. The stoichiometric number was obtained from transients considerably exceeding the linear region.