Membrane contactors have been used in a wide range of applications, since they offer a number of advantages over the conventional dispersed phase contactors, such as the absence of emulsions, no flooding at high flow rates or unloading at low flow rates. Besides, they provide a very high and constant specific interfacial area. Hollow fibre modules have been the preferred geometry when liquid-liquid and gas-liquid interfaces are involved. This paper addresses a novel application for hollow fibre membrane contactors. A microporous hydrophobic hollow fibre membrane module is used as an interface for membrane inlet mass spectrometry (MS). The module acts as a gas contactor between the liquid phase in which a gaseous or volatile analyte is dissolved and a stripping gas that is analysed by MS. The signal of the mass spectrometer is thus correlated to the concentration of the analyte in the liquid phase. The performance of the developed system was tested by measuring the concentration of dissolved oxygen, propane and ethanol in water. Linear correlations were obtained between the mass spectrometer signal and the concentration of the dissolved analytes. The effect of operation parameters such as liquid and gas flow rates and membrane area on the module performance and on the mass spectrometer signals was studied. This type of interface, by enabling liquid phase analysis, might prove an useful and low cost upgrade of instruments designed and constructed to exclusively analyse gas phases.