A fiber optic sensor for halides was constructed based on the collisional quenching of quinolinium chromophores bound to porous glass beads. The halide indicators N-(4- aminobutyl)-6-methoxyquinolinium (ABQ) and N-(7-carboxyheptyl)-6-methoxyquinolinium (CHQ) were covalently attached to surface derivatized glass beads. The labeled beads were fluorescent with excitation and emission maxima at 350 and 450 nm, respectively. Halide sensitivity and kinetics were examined by epifluorescence microscopy of immobilized beads. The CHQ labeled beads had a higher sensitivity to halides than the ABQ beads. CHQ bead fluorescence was quenched at 100 mM halide concentration by 40% for Cl-, 55% for Br-, 80% for SCN-, and 85% for I-. The 10 - 90% rise time for a step change in chloride concentration was approximately 4 s. Similar results were obtained when the beads were cemented to the tip of a single quartz fiberoptic. Time-resolved microfluorimetry studies showed that nanosecond fluorescence lifetimes decreased with halide concentration.