A comparison is made of drop diameters produced by disk impellers having two, four, six and eight blades, all of the same impeller diameter and rotated at the same speeds. Measurements in situ at rotational speeds between 250 and 560 RPM and at hold-up fractions 0.01, 0.025, 0.07 showed that the Sauter mean drop diameters increase with the decrease of number of impeller blades and this increase may reach up to 52%. Plots of In d(32) versus In N, In d(32) versus In n and d(32) versus d(max) gave straight lines.