A review is given of recent work on the measurement of droplet coalescence and breakage rates in a packed and a pulsed plate extraction column using a newly developed colorimetric technique. The results, which were interpreted in terms of second order coalescence and first order breakage rate constants, showed that the droplet interaction rates are considerably lower in the pulsed column. The rate constants can also be used to predict accurately the steady state droplet size distribution, and to study theoretically the effect of droplet coalescence and breakage on mass transfer rate. Deficiencies in the available mass transfer coefficient data for droplets, both individual and in “swarms”, are pointed out.