The Self-cycling fermentation (SCF) technique was applied to the biodegradation of several aromatic compounds by Pseudomonas putida and Pseudomonas fluorescens. The SCF technique was shown to hate several advantages over the sequential batch reactor and other methods of biodegradation. The SCF technique allowed stable and repeatable performance over an extended period of time, with almost complete substrate consumption. The system was flexible acid easily adapted to changes in concentration and/or type of substrate. The rates of consumption were considerably higher than reported for any other biodegradation technique.