The absorption of CO2 at a plane interface by water and aqueous solutions of surfactants was measured in the presence and in the absence of Marangoni effect induced by deposition of a variety of liquids of low surface tension on the gas-liquid interface. Measurement of the induced surface velocity distribution allowed mass transfer in the presence of induced convection to be related to interface hydrodynamics by correlation of Sherwood and Reynolds numbers, and also allowed the calculation of surface residence times for which the divergent interfacial flow in the experimental apparatus was taken into account. When used in Higbie’s equation the residence times afforded theoretical mass transfer coefficients which, for water as absorbent liquid, were within 4% of the experimental values. Surfactants were found to modify absorption not only through their hydrodynamic effects, but also by some other mechanisms, which was nevertheless estimated to contribute only about 15% of the total resistance to mass transfer in the presence of surfactant.