Two different mixed cultures, which degrade terephthalate at 50 degreesC and pH 8, were isolated from a wastewater treatment plant. These were useful for the treatment of wastewater containing a high concentration of terephthalic acid (TPA). Each mixed culture included a TPA-degrading bacterium, strain K1 or Pseudomonas sp.,C4S, and another bacterium unable to degrade TPA, the as-yet unclassified strain K3 or Bacillus sp: C4B. In axenic culture, K1 and C4S showed poor growth even ih a medium supplemented with yeast extract and tryptone. On the other hand, when co-cultured with the co-isolate from the mixed culture which is unable to degrade TPA, the growth was enhanced. Moreover, several bacterial strains in our stock culture collection showed the ability to improve the growth of both TPA-degrading bacteria. A mixed culture of strains K1 and K3 exhibited rapid growth and TPA degradation in a chemically defined medium, suggesting that the mixed culture system would be applicable to the treatment of wastewater containing TPA.