A technique for the detection of methyl-tert-butyl-ether (1634044) (MTBE) in gasoline vapors and liquid gasoline was described. Optimal gas chromatographic conditions for the separation of MTBE were determined and the precision and linearity of MTBE standards over an extended concentration range covering the expected level of MTBE in gasoline was evaluated quantitatively. Technique variables including sample collection using tandem charcoal tubes, the MBTE extraction procedure, and MTBE recovery, storage, stability, and breakthrough volume were assessed and optimized. Personal breathing zone samples obtained from various service stations and 75 samples of different grades of gasoline were analyzed using this system. MTBE as well as methanol (67561), ethanol (64175), benzene (71432), hexane (110543), toluene (108883), m-xylene (1330207), and p-xylene were resolved using this method. MTBE levels in gasoline samples ranged from nondetectable to 21% and mean MTBE personal exposures ranged from 0.14 to 0.32 parts per million. The authors conclude that the method described was useful for the determination of MTBE collected from air samples.