An acclimated activated sludge was examined for its ability to degrade 3-fluorophenol in aerobic batch cultures. The result indicated that the organism degrades up to 100 mg/L 3-fluorophenol completely with approximately 100% fluoride anion release within 16 h. 3-Fluorophenol can serve as the sole carbon source and energy source for the organism. The acclimated activated sludge can degrade 3-fluorophenol effectively. The degradation mechanism study reveal that the initial step in the aerobic biodegradation of 3-fluorophenol is its transformation to fluorocatechol. Following transformation of the fluorophenol to fluorocatechol, ring cleavage by catechol 1, 2-dioxygenase proceedes via an ortho-cleavage pathway, then defluorination occurres.