Two-phase structures within an aerated-liquid injector and the near field of the discharged jets were characterized, using the X-ray radiography and fluorescence techniques. The X-ray source available at the 7-BM beamline at the Argonne National Laboratory was used for the present study. The axisymmetric aerated-liquid injector is made out of beryllium, due to its high X-ray transmittance. Krypton and bromine were added into nitrogen and water, respectively, at low concentrations for fluorescence generation along a well-focused X-ray beam positioned inside the injector or the aerated-liquid jet. The obtained line-of-sight fluorescence signals were further processed to account for signal trapping to give quantitative mass distributions at various injection conditions. For the first time, formation and evolution of the two-phase mixture inside the beryllium aerated-liquid injector with a given injection condition and fixed injector geometry were successfully characterized with quantitative liquid mass distributions. The present X-ray measurements also give quantitative liquid and gas mass distributions within the discharged aerated-liquid jets at various injection conditions. The mass distribution profiles show that the gas plume is separated from the liquid plume within the discharged aerated-liquid jet. The width of the gas plume is narrower than that of the liquid plume, especially at the downstream locations for welldispersed sprays. It was also found that the liquid mass distribution within the aerated-liquid jet transitions from a co-annular structure to a uniform structure as both liquid flow rate and aeration level increase. The potential mechanisms for the separation of liquid and gas plumes were proposed and discussed in the present study.