As a preparation of the procurement of Low Frequency Active Sonar (LFAS) systems, the Royal Netherlands Navy and TNO are developing an interim system, which is compact and flexible in the sense that it can be easily installed on and removed from almost any platform. This Interim Removable LFAS system will be operated during naval exercises. It will also serve as a vehicle for further (multi-static) LFAS research and development activities in the Netherlands for the coming years. The wet-end of the system consists of the TNO SOCRATES source and a towed triplet array. The dryend is fully containerized and is build from COTS hardware including PC’s. The software has a fully openarchitecture and is therefore easily adaptable to future demands. The IRLFAS system was successfully taken to sea for sea-acceptance test and operational evaluation on a frigate in fall 2005. The system architecture as well as the results of these first tests are presented in this paper.