Abstract: Groundwater was mixed with phosphate buffer of pH 7.4, ethanol and surfactant and analyzed by continuous-flow immunosensors CFI), combining the highly selective antibody-antigen binding interaction with the sensitivity of fluorescence spectroscopy as the signal generation mechanism. The CFI was a semi-automated system in which the groundwater was pumped through a column containing antibodies raised against the analyte which were covalently attached to small plastic beads. As the analyte passed through the antibody matrix, some of the fluorescent dye-labelled explosive analogue was displaced from the antibody in favour of binding the analyte. The two most commonly used military explosives: 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) were detected by the method and quantified fluorimetrically. Field testing of the immunosensor proved its usefulness as a faster, less expensive and portable alternative to HPLC.