The extraction of 15 aroma compounds from. a highly diluted aqueous feed with hollow fiber membrane contactors was investigated. Membrane-Based Solvent Extraction (MBSE) and Membrane Air-Stripping (MAS) were tested with the aqueous feed cross-flowing on the shell side and the stripping phase flowing in the lumen of the hollow fiber. Experimental results showed that globally, MBSE offered higher overall mass transfer coefficients than MAS. This difference was mainly explained by the gap in partition coefficients. Hexane-water partition coefficients were about 10,000 times higher than air-water partition coefficients. The contribution of each local resistance to mass transfer was identified by a resistance-in-series model. Mass transfer in the aqueous feed boundary layer is the limiting step in MBSE, while mass transfer in the stripping gas boundary layer is the limiting step in MAS. A diagnostic tool based on partition coefficients was developed in order to help choose the adequate process for the extraction of an aroma compound. (c) 2006 American Institute of Chemical Engineers.