A 5 cm internal diameter Karr reciprocating plate column has been operated in countercurrent liquid-liquid flow in the absence of mass transfer and with mass transfer of i-propanol from the dispersed phase (Isopar M) to the continuous phase (water). The effect of mass transfer is to increase the drop diameter, while the holdup is reduced and axial dispersion is increased. Although an unstable density gradient was created by the mass-transfer process, earlier models developed under non-mass-transfer conditions, based on Kolmogoroffs isotropic turbulence theory, were not applicable in describing the enhancement in axial mixing. It was concluded that the density gradient effect was masked by the effect of the larger drops which were formed because of mass-transfer-induced coalescence. Mass-transfer coefficients for the dispersed phase were found to show the same trends as the Handles and Baron oscillating drop model.