A new analytical method, the membrane extraction with a sorbent interface (MESI) technique, has been developed to allow practical applications of multiplex gas chromatography for environmental monitoring of volatile organic compounds (VOCs). The advantages of the multiplex-MESI system include simplicity, durability, low cost, time efficiency, elimination of solvents and easy automation. The background and principles of the system are reviewed and potential applications and limitations of the multiplex-MESI system are discussed.