Experiments are conducted in a bubble column reactor with inner diameter of 970mm at atmospheric pressure with an air/water system at height-to-diameter ratios of 1 and below. Axial and radial dispersion coefficients are measured using a tracer, which is detected by conductivity probes. An analytical mathematical model for the determination of the dispersion coefficients from the experiments is presented. The measurements show the determined axial dispersion coefficients to vary significantly over the height of the column while increasing linearly with the gas flow rate.