In a liquid-liquid agitation system containing a surface-active agent, transient size distributions of emulsion drops were measured at various impeller speeds after the initiation of agitation. The absence of drop coalescence in the system was confirmed experimentally. In breakup processes at each impeller speed, drop size distributions revealed a similar distribution form. The evolutions of Sauter mean drop sizes in the present work were compared with previous ones that were obtained in breakup processes in a range of relatively large drop sizes. It was found that the present data showed time-variation similar to that of the previous data. A new correlation equation, which expresses the evolution of Sauter mean drop size over a wide range of drop sizes, was proposed.