Repairing and replacing of worn-out underground pipes, such as sewer pipes, water-supply pipes, gas pipes, and communication cables by excavating not only cause traffic congestion but also produce large amount of waste. Also, the operation requires heavy equipments and longer operating time and high cost. In this study, the repairing-reinforcing process of underground pipes with glass fiber fabric polymer composites using resin transfer molding (RTM) which overcomes the problems of present trenchless technologies has been developed. The developed process requires shorter operation time and lower cost with smaller and simpler operating equipments than conventional trenchless technologies. For the faultless operation. a simple method to apply pressure and vacuum to the reinforcement was developed. The resin wetting and void removal during RTM process for very large and long-composite buried pipes were experimentally investigated, and the efficient void removal method was suggested. Cure status and resin filling were monitored with a commercial di-electrometry cure monitoring system, LACOMCURE. From the investigation, it has been found that the developed repair technology with appropriate process parameters and on-line cure monitoring has many advantages over conventional methods. (C) 2002 Published by Elsevier Science Ltd.