SummaryGas chromatography (GC) with photoionization (PI) and Hall electrolytic conductivity (E1C) detectors connected in series, has been used for the determination of chlorofluorinated oleflns. The separation of different standard solutions containing eight chlorofluorinated ethenes in nitrogen and in halogenated matrices has been performed in wide bore capillaries, 0.53 mm i.d,. and normal capillaries, 0.32 mm i.d.. The quality of separation is obviously influenced by their limited load capacity and by the response time of the Hall detector. At concentrations 1-150 jaL L -1 halogenated olefins, both PI and E1C detectors have linear response and can detect minimum levels of 0.2-0.5 ng and 0.4-1.2 ng, respectively. The PID is particularly selective toward halogenated olefins and is extremely useful for the determination of traces of unsaturated halogenated hydrocarbons in a matrix of saturated homologues. The results of this work are of great interest for the detection of chlorofluorinated oleflns, highly toxic compounds usually formed as by-products in the industrial production of hydrofluorocarbons and hydrochlorofluorocarbons.