The heat of transport for passage of matter through a gas-liquid interface has been determined for the aniline liquid-vapour system, by measuring stationary-state pressure differences produced by known temperature differences over a distance of 2 nun on the vapour side of the interface. For the range of pressures used, 2 mm, is between 6 and 34 mean free paths. Coupling of the heat and matter fluxes is significant over the whole of this range. At the higher pressures the heat of transport is more than 20% of the heat of condensation; at the lower pressures it is more than 50%. (C) 2002 Elsevier Science B.V. All rights reserved.