2-Hydroxybenzothiazole (OBT) is present in wastewaters from the industrial production of the rubber vulcanization accelerator 2-mercaptobenzothiazole (MBT). We have achieved the first isolation of axenic bacterial cultures capable of the degradation of OBT and growth on this substrate as the sole source of carbon, nitrogen and energy. All isolates had similar characteristics corresponding to one particular isolate, which was studied in more detail and identified as Rhodococcus rhodochrous. The strains were also capable of degrading benzothiazole (BT) but not MBT or benzothiazole-2-sulphonate (BTSO3). OBT was degraded at a concentration of up to 600 mg.l(-1). BT was toxic above 300 mg.l(-1). MBT inhibited OBT degradation. Growth on OBT was not significantly different at pH values of between 6.3 and 7.9 or salt concentrations between 1% and 3%. In shake flasks the cells clumped together, which resulted in a lower rate of oxygen transfer and slower degradation as compared to cells grown on OBT in a stirred reactor.