Abstract: A method and apparatus for sequential launching a plurality of pipeline pigs in serial manner into a gas transmission pipeline. The pig launching system incorporates a tubular magazine for receiving a plurality of pigs and having a free piston movably disposed therein. A source of hydraulic fluid medium is provided and is injected into the magazine behind the free piston for movement of the free piston and the pigs for pig launching. A gas energized liquid pump is operated by gas pressure from the gas transmission pipeline under the control of a timer operated gas supply valve for selective introduction of hydraulic fluid medium into the magazine. A control panel incorporating control circuitry is programmable to achieve timed launching of the pigs into the pipeline and shuts down the pig launching mechanism after each pig has been launched. The control circuitry is also capable of rendering an alarm signal if pig launching is not achieved within a predetermined time period.