Gas hold-up and bubble size distribution in a slurry bubble column (SBC) were measured using the advanced noninvasive ultrafast electron beam X-ray tomography technique. Experiments have been performed in a cylindrical column (D-T = 0.07 m) with air and water as the gas and liquid phase and spherical glass particles (d(P) = 100 mu m) as solids. The effects of solid concentration (0 <= C-s <= 0.36) and superficial gas velocity (0.02 <= U-G <= 0.05 m/s) on the flow structure, radial gas hold-up profile and approximate bubble size distribution at different column heights in a SBC were studied. Bubble coalescence regime was observed with addition of solid particles; however, at higher solid concentrations, larger bubble slugs were found to break-up. The approximate bubble size distribution and radial gas hold-up was found to be dependent on U-G and C-s. The average bubble diameter calculated from the approximate bubble size distribution was increasing with increase of U-G. The average gas hold-up was calculated as a function of U-G and agrees satisfactorily with previously published findings. The average gas hold-up was also predicted as a function of C-s and agrees well for low C-s and disagrees for high Cs with findings of previous literature. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 1709-1722, 2013