A headspace solid-phase dynamic extn. method coupled with gas chromatog.-mass spectrometry (HS-SPDE-GC/MS) for trace volatile halogenated hydrocarbon and benzene detn. in groundwater was developed and evaluated. As target compds., benzene and 11 chlorinated and brominated hydrocarbons (vinyl chloride, dichloromethane, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, CCl4, chloroform, trichloroethylene, tetrachloroethylene, bromoform) of environmental and toxicol. concern were studied. Analytes, extd. with a SPDE needle device coated with polydimethylsiloxane with a 10% embedded activated C phase (50-mm film thickness and 56-mm film length), were analyzed by GC/MS in full-scan mode. Parameters affecting extn. yield (extn. and desorption temp., salting-out, extn. and desorption flow rate, extn. and desorption vols., no. of extn. cycles, pre-desorption time) were evaluated and optimized. Linearity of the HS-SPDE-GC/MS method was established over several orders of magnitude. Method detection limits (MDL) for studied compds. were from 12 ng/L fir cis-dichloroethylene and trans-dichloroethylene to 870 ng/L for vinyl chloride. The method was thoroughly validated, and its precision at 2 concns. (0.1 mg/L and a concn. 5 times above the MDL) was 3.1-16% for studied analytes. SPDE provided high sensitivity, short sample prepn. and extn. times, and high sample through-put due to full automation. Applicability to actual environmental samples was exemplarily for groundwater samples from a former waste-oil recycling facility. Site groundwater was a complex contamination with chlorinated volatile org. compds. and arom. hydrocarbons.