A new invasive sensing probe for the measurement of local phase holdups in two- and three-phase reactors is described. The local gas and solids holdups in a bubble column with a volume of V = 2 m(3) at varying operating conditions (gas velocity, sparger design, solids content and density) are measured by means of differential pressure measurement in combination with either time domain reflectometry or electrical conductivity measurement. The phase distribution profiles at two- and three-phase operating conditions are described. The influence of the sparger design on the shape of these profiles, the influence of the solid phase on the gas distribution, the solids distribution and the gas-stow effect above the sparger because of a dense particle layer are capable of experimental proof for the first time.