Reliable on-line analysis of production gas composition is fundamental to the success of an in situ extraction experiment in Antrim shale. An automated sampling and analysis system designed to meet this need has provided high quality analytical data for three extraction trials without a single day when no data were taken. The production gas samples were routinely analyzed by both gas chromatography (GC) and a bank of continuous on-line process gas analyzers. The GC's analyzed for H/sub 2/, O/sub 2/ Ar, N/sub 2/, CO, CO/sub 2/, SO/sub 2/, H/sub 2/S, individual C/sub 1/ - C/sub 5/ hydrocarbon species, and lumped C/sub 6/ hydrocarbon species, each analysis requiring up to an hour to run. The process gas analyzers measured CO, CO/sub 2/, total hydrocarbons (% vol CH/sub 4/ equivalent), and O/sub 2/ continuously. The process gas analyzers were shown to be especially well suited for this application because of their fast response. The GC data provided itemized composition details as well as an independent check of process analyzer data. Sample selection, data collection and processing from both the GC's and process gas analyzers was handled by a Perkin Elmer Sigma-10 minicomputer. The combination of the two analytical techniques and automated data handling yielded a versatile and powerful system. The production gas sampling system demonstrated the feasibility of transmitting a properly treated gas sample through a long (1000 ft) 1/8''diameter sample line. The small bore tubing allowed the analytical instruments to be located a safe distance away from the well heads and yet maintain a reasonably short sample transport lag time without handling large volumes of gas.