Velocity distributions adjacent to the interface between a water-drop and surrounding oil were measured using PTV. By analyzing the measured velocity data the physical properties such as surface slip conditions, circulating flow in a drop, distributions of contamination skin, are quantitatively obtained.Relating to the heat and mass transfer in multi-phase flows, information about microscopic phenomena occurred at the interface of fluids has been estimated so far from macroscopic measurements. Difficulties to directly measure the phenomena on the interface come from their special conditions of moving boundaries, transient, and spatially distributed phenomena. Most of those difficulties can be resolved by the PTV technique. Since it is the quantitative visualization method, only if some of those phenomena can visually captured, it is not difficult to obtain a part of the required information
