The chemiluminescence of luminol in the presence of H2O2 has been exploited to develop fiberoptic biosensors associated with flow injection analysis systems. A chlorophenol sensor was developed based on the ability of certain halophenols to enhance the peroxidase-catalyzed luminol chemiluminescence. Horseradish peroxidase immobilized on a collagen membrane was used. Ten chlorophenols have been tested with this chemiluminescent-based sensor. The lower detection limit was obtained with 4-chloro-3-methylphenol and was equal to 0.01 muM. Electrochemiluminescent-based fiberoptic biosensors for glucose and lactate were also developed using glucose oxidase or lactate oxidase immobilized on polyamide membranes. In the presence of oxidase-generated H2O2, the light emission was triggered electrochemically by means of a glassy carbon electrode polarized at +425 mV vs a platinum pseudo-reference electrode. The detection limits for glucose and lactate were 150 and 60 pmol, respectively, and the dynamic ranges were linear from 150 Fmol to 600 nmol and from 60 pmol to 60 nmol, respectively.