A module was developed for the continuous monitoring of volatile halogen organic pollutants in complex matrices. The module utilized a polymer membrane for extraction and a capillary gas chromatography-mass spectrometry (GC-MS) for detection. The extraction of analytes (CHCl(3), CHCl(2)Br, CHClBr(2) and CHBr(3)) from samples was performed in a flow system mediated by a non-porous flat membrane. The effects of the phase-volume ratios, flow conditions, kinetics, analyte properties and matrices were assessed and optimized. The limits of detection were at low microg L(-1) to ng L(-1) levels, with GC-MS analysis under selected ion monitoring (SIM), whereas enrichment factors between 6 and 30 were achieved. Precision values calculated as repeatability and reproducibility with a relative standard deviation (%RSD, n = 5) of 7.2 to 9.5 after 30 min were obtained. The performance of the continuous membrane assisted solvent extraction system was compared with classical liquid-liquid extraction. The method was applied to the extraction of trihalomethanes in chlorinated drinking-water samples.