A new optical fiber sensor for tetracycline is fabricated with an anthracene-containing copolymer prepared from 9-anthrylmethyl methacrylate, methyl methacrylate and n-butyl acrylate (PAMB). The sensing relies on the fact that the fluorescence of the sensor membrane fabricated with PAMB can be strongly quenched by the tetracycline antibiotics extracted from the sample. The proposed sensor responds linearly in the measuring ranges 2.02 x 10(-7)-2.02 x 10(-4) mol l-1 tetracycline (TC), 2.00 x 10(-7)-2.03 x 10(-4) mol l-1 oxytetracycline (OTC) and 4.05 x 10(-7)-2.03 x 10(-4) mol l-1 doxycycline (DC) and has detection limits of 1.00 x 10(-7) mol l-1 for TC and OTC, and 2.00 x 10(-7) mol l-1 for DC. The leaching of anthracene from the sensor membrane was hindered by covalent immobilization, resulting in a drastically enhanced sensor lifetime. Moreover, the sensor can rapidly respond to the antibiotics of interest (ca. 30s) and exhibits good reproducibility, reversibility, and selectivity in the presence of some common pharmaceutical species as well as alkali and alkali-earth metal salts. The sensor was used for the direct assay of tetracycline antibiotics in commercial pharmaceutical preparations and urine. The results are comparable to those obtained by conventional spectrophotometry. The recovery for tetracycline antibiotics from urine samples is also satisfactory.