1. 2-Chlorosyringaldehyde (2-CSA) is the major chlorinated phenol produced by the 100% chlorine dioxide bleaching of eucalypt pulp and is found in other bleached hardwood effluents. Almost nothing is known of the environmental or metabolic fates of this chemical. 2. Sand flathead (Platycephalus bassensis) was given 2-CSA by intraperitoneal injection at 0.15,1.5, 15 and 75 mg/kg doses and, 4 days later, bile was collected and solvent extracted before and after enzymatic cleavage of conjugates. The acetate derivatives of bile extracts were analysed by gas chromatography/mass spectrometry. 3. The major metabolite 4 days after administration was the glucuronide or sulphate conjugate of 2-chloro-4-hydroxy-3,5-dimethoxy-benzylalcohol (2-CB-alcohol). The identity of 2-CB-alcohol was confirmed by chemical synthesis. 4. The quantity of 2-CB-alcohol in the bile was linearly related to dose of 2-CSA and was detected at all dose levels. Minor metabolites identified were conjugated 2-CSA. unchanged 2-CSA and 2-chloro-4-hydroxy-3,5-dimethoxy-benzoic acid. 5. The amount of 2-CB-alcohol in bile has the potential to be a sensitive and specific indicator of fish exposure or bleached hardwood effluent.