An instrument employing a light addressable potentiometric sensor and a flow-through immunofiltration-enzyme assay system has been developed for the rapid and specific identification of biological warfare (BW) agents. The system has been designed to assay for up to eight agents simultaneously and provides an indication of the absence or presence of a threat within 15 min. Parameters affecting the mixing of the reagents within the instrument's fluidic lines were investigated and optimized. Measurements of blank samples and samples containing Bacillus subtilis spores in the concentration range of 10(4) to 10(6) cfu/ml indicate the limit of detection (LOD) is 3 x 10(3) cfu/ml for B. subtilus. Although the LOD is higher than that of several technologies currently under development, this instrument offers an immediate interim approach for addressing the need to rapidly detect biological warfare agents in the field.