A bacterium isolated from sludge from dyeing wastewater treatment which removed the colour of reactive azo dyes arch as Red G, RBB, RP(2)B and V(2)RP was identified as P. luteola. After shaking incubation for 48 h, P. luteola removed the colour of these dyes during a further 2 days of static incubation, and the fraction of decolourization was 37.4% (Red G), 93.2% (RBB), 92.4% (RP(2)B) and 88% (V(2)RP). There was no increased removal of colour when P. luteola was cultured in a low-N medium. No colour was removed under continuous shaking or completely static incubation. According to results from a thin-layer chromatogram, Red G was not degraded and reduction of the azo bond (-N=N-) was the major reason for its decolourization. An extra two spots appeared on the TLC for the other three reactive dyes, which indicated that they were degraded by P. luteola; the azoreductase activity was high when RBB was the substrate, but sulphanilic acid was not found in the metabolites.