The potential of MIMS (membrane introduction mass spectrometry) to study pervaporation processes through a polydimethylsiloxane (PDMS) membrane is demonstrated. From the MIMS profiles of aqueous alcohol solutions (ethanol, propan-1-ol, propan-2-ol, butan-1-ol, 2-methylpropan-2-ol, pentan-1-ol, 2-methylbutan-2-ol, cyclohexanol), diffusion coefficients and fluxes were calculated. The diffusion of chloroform, phenol, toluene and chlorobenzene was also studied. Selectivity (α) and enrichment (β) pervaporation factors have been obtained for ethanol–water solutions.