Two-phase hydrodynamics has been experimentally investigated using optical fibre probes in individual channels of a laboratory scale monolith bed. Experimental investigations were carried out to validate the optical probe measurements in a single capillary. Optical probes were positioned at selected single channels of a monolith block, and the signals were processed to assess the local hydrodynamics under cocurrent gas-liquid downflow configuration, using air and water as fluids. The investigations were performed for three different distributors, viz. single pipe, multipipe, and packed bed distributor configurations. The different distributor configurations were evaluated on the basis of void fraction and bubble frequency for a wide range of flow velocities. The specific novelty aspect of this study comes from the fact that we have undertaken channel scale investigations in monoliths under conditions where we have also reported the global gas-liquid distribution. Thus, one can readily correlate the bed-scale hydrodynamics with the local channel-scale hydrodynamics. (c) 2016 American Institute of Chemical Engineers AIChE J, 63: 327-336, 2017