A 15 cm diameter reciprocating plate column has been operated under gas-liquid flow conditions with a stack of doughnut-type plates having inner and outer diameters of 7.5 cm and 13.0 cm, respectively. Axial dispersion coefficients and gas holdup have been measured. It Is found that this type of plate gives lower axial dispersion coefficients than a previously tested doughnut plate having an outer diameter almost the same as the column internal diameter, but the gas retention times are slightly lower.