Hydrodynamic parameters have been determined in common equipment, i.e., same column and liquid and gas distributors, for cocurrent and countercurrent two-phase flow through fixed beds. The piston/dispersion exchange model (PDE) with usual Danckwerts＇ boundary conditions (closed/closed system) has been used to describe the liquid flow. A new imperfect pulse method has been used to estimate the PDE model parameters directly from the experimentally nonideal input and output response. The transition between trickle flow and pulse flow, for two-phase downflow, and the occurrence of flooding, for countercurrent flow, has been investigated using a macroscopic model for the two-phase flow.