A review of the research works on the dynamic operation of the three phase catalytic reactor is presented. Two cases were examined: the start up of the chemical reactor and the forced oscillation of inlet quantities (reactant concentrations, flow rate etc.). Criteria for the definition of the reference steady state to compare with the unsteady state process are discussed. For complex reactions of industrial interest the effect of the accumulation rate on yield and selectivity is studied; in some cases variation of the period time and split of the pulsing inlet quantity was considered. A critical discussion of the results of the dynamic operation in three phase catalytic reactor shows that the best advantages are obtained by forcing the liquid inlet flow rate.