Abstract: Hydrodynamics in rotating perforated disk contactors (RPDC) have been studied with kerosine-water and emulsion-water systems. The effects of the contactor dimension and the two phase systems on the fractional hold-up X and the characteristic velocity u as well as the rotor speed at flooding nt have been studied. The contactor dimension factors investigated are: (1) the diameter of stator ring opening, (2) the diameter of the disk and the hole distribution on it, and (3) the hole size. Experimental results indicate that: (1)for a given system, when contactor dimension and rotor speed remain unchanged, the phase flow rates, the holdup and the characteristic velocity can be correlated by the semi-empirical equation proposed by logsdial: u + ucx/(1 - x) =uox(1 - x) (2) at slow rotor speed, RPDC has good liquid-liquid dispersion performance, as the rotor peripheral speed was about 0.5m/s, (only 1/3 of the critical rotor peripheral speed of RDC), the change of the fractional hold-up x andthe characteristic velocity uo with the rotor speed n was very pere This is due to the fact that holes on the rotor disk have good cutting ef on the dispersed phase drops that are going up through the holes, (3)the minimum rotor speed under which the holes can cut the dispersed phase drops may be calculated as tollows: