Mass transfer coefficient data are presented for the transfer of solutes between isolated drops and continuous phase in a droplet file column. Radioactivity labelled, i.e. tritiated water was used as a tracer to obtain values of the individual phase coefficients in saturated binary systems. Those for the continuous phase were found to be satisfactorily represented by the Garner-Tayeban correlation, and a new model, based on the introduction of inertia into that of Kronig and Brink, was developed for the dispersed phase. Data were also obtained for the transfer of both bulk and C-14-labelled acetic acid between methyl isobutyl ketone (MIBK) and water, and the resulting overall coefficients were compared with those predicted from the individual coefficient data. Agreement was good for bulk transfer into the drops, but those for transfer out of the drops were enhanced by a factor of 2-3 by Marangoni instability, as expected. A similar enhancement was also observed, surprisingly, for tracer transfer out of MIBK drops, but not out of water drops.