Fluctuation analysis in electrochemical systems appears to be a suitable method for obtaining information on the system dynamic behaviour, especially when the voltage or current fluctuations are due to elementary events on the electrode at a semi-macroscopic scale, for example growth and detachment of bubbles on a gas-evolving electrode or contacts between charged particles in a fluidized or circulating bed reactor, or pits in localized corrosion. Therefore this situation is largely encountered in electrochemical engineering processes with two phase flows. By analysing the current (voltage) fluctuations at constant potential (current) and/or the electrolyte resistance fluctuations, this technique provides quantitative parameters which are often inaccessible by traditional deterministic techniques, steady state or not, which deal with time-averaged signals. The technique also leads to a better understanding of the elementary processes on the electrode. Two examples are given: the first concerning a gas-evolving electrode and the second a circulating bed electrode.