The invention relates to a method for producing pentafluoroethane, and especially to a method comprising (i) a step during which perchloroethylene and optionally 2,2-dichloro-1,1,1-trifluoroethane and/or 2-chloro-1,1,1,2-tetrafluoroethane react(s) with hydrofluoric acid in a gaseous phase in the presence of a catalyst in an adiabatic multi-stage reactor, and optionally (ii) a step of separating the flow produced in step (i) in order to obtain a fraction of light products and a fraction of heavy products.