The paper presents results of an experimental study of the hydrodynamics of a counter-current packed bed column undergoing a step change in the inlet velocity of the gas phase. The experimental transient curves are presented for the total pressure drop across the column and the pressure profile along the column height. Characteristic overshoots have been observed on the transient curves of the pressure drop and pressure profiles within the bed when the irrigated bed is suddenly exposed to the Bow of gas. These rather unexpected overshoots appear temporarily after the onset of gas flow and cannot be explained by existing two-phase flow models.