Sol-gel-derived mesoporous biomaterials were used for the first time in the flow-injection fluorescence immunoassay system. Anti-gentamicin antibody was immobilized in a mesoporous sol-gel material using tetramethoxysilane as a precursor and poly(ethylene glycol) as a template. The sol-gel glass was used to develop an immunoaffinity column for the flow-injection immunoassay of gentamicin. Little unspecific adsorption of gentamicin on the sol-gel and no antibody leaching under harsh elution conditions were found. The immunoassay is based on the competition between gentamicin and fluorescein isothiocyanate-labeled gentamicin for a limited number of encapsulated antibody binding sites. NaOH solution of 5 x 10(-3)mol/L is used for the regeneration of encapsulated antibody binding sites after each measurement, which allows the immunoreactor to be used for up to 20 times without any loss of reactivity. Sample preconcentration is not needed and a single assay can be performed within 10 min. The calibration for gentamicin has a working range of 250-5000 ng/mL with a detection limit of 200 ng/mL, which is close to that of the fluorescence immunoassay and fluorescence polarization immunoassay using the same reactants. Comparison of the results from this method with that obtained from HPLC showed an excellent correlation.