Biodegradation of carbazole was enhanced by the presence of a non-aqueous phase liquid (logK(o/w) greater than or equal to 3.1) at phase ratio of 1: 1 (organic/aqueous). In a cyclohexane/aqueous phase system, the maximum specific degradation rate (3.34 mg carbazole min(-1) g dry cell(-1)) was at an organic/aqueous ratio of 1:1. Pseudomonas sp. XLDN4-9 degraded 47% (w/w) of 1 g carbazole l(-1) in cyclohexane phase directly within 1 h.