Pseudomonas testosteroni CPW301 degraded phenol and 4-chlorophenol simultaneously, but degradation rates of these compounds were affected by 4-chlorophenol. Phenol increased the cell concentration and therefore the degradation efficiency of 4-chlorophenol was improved. Pseudomonas solanacearum TCP114 could degrade only 2,4,6-trichlorophenol. A defined mixed culture of P. testosteroni CPW301 and P. solanacearum TCP114 could treat phenol, 4-chlorophenol, and 2,4,6-trichlorophenol completely and overcome the inhibition of substrates to other microorganisms. The degradation capacity of the packed bed reactor (PBR) was higher than that of the continuous stirred tank reactor, but the PBR was unsuitable for oxygen-sensitive microorganisms. (C) 2002 Elsevier Science Ltd. All rights reserved.