Isolated Gram-negative bacteria, being capable of degrading toxic, recalcitrant, and pigment-producing furfural, were tentatively identified as Pseudomonas testosteroni, Pseudomonas maltophilia, Klebsiella Pneumoniae, and Pseudomonas fluorescens. They exhibited synergistic effects between P. testosteroni and the others in the degradation of colourproducing furfural. Synergistic effects and possible sequence of its degradation were attempted by manometric technique. P. testosteroni could degrade furfural to decolourize it and produce ninhydrin-reaction postive substance (NPS) which could be utilized by P. maltophilia and K. pneumoniae and the latter two bacteria could ,degrade furfural to 2-furoic acid as an oxidized form. Finally 2-furoic acid was further oxidized by P. fluorescens. Once NPS and 2-furoic acid were produced, the degradation efficiency was enhanced by competing four bacteria against furfural and 2-furoic acid.