Hydraulic jumps are commonly experienced in industrial applications and manufacturing processes, as well in rivers and canals. The hydraulic jump is the sudden transition from a high-velocity open channel flow to a subcritical flow motion. Despite nearly two centuries of studies, there is still a lack of knowledge on the two-phase flow properties of the turbulent shear layer and the roller. New series of experimental measurements were conducted in hydraulic jumps with Froude numbers between 5 and 8.5, and inflow Reynolds numbers between 38,000 and 62,000. The two-phase flow measurements included some vertical profiles of void fraction, bubble count rate, interfacial velocity and bubble chords. In the air-water shear region, the void fraction and bubble count rate distributions exhibited marked peaks, with the maximum of void fraction always above the location of the maximum bubble count rate. The dimensionless turbulent diffusivity coefficient was estimated. The dimensionless distributions of interfacial velocity compared favourably with some wall-jet flow equations. The data analysis showed that the mean bubble chord in the turbulent shear layer was between 1 mm and 6 mm. The probability distribution functions (PDF) of bubble chord time illustrated a broad spectrum with predominance to small bubbles compared to the mean. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.