An electronic nose based on a non-specific conducting polymer array was evaluated against sewage odour concentrations From ten sewage treatment works. Sensor responses from the twelve sensor array were compared using canonical correlation (a data reduction technique) with threshold odour numbers (TON) made by dynamic dilution olfactometry. The results suggest that for sewage odours from a range of locations within different treatment works, no universal relationship is present, whereas a strong correlation can be produced between TON and the electronic nose responses (as represented by a canonical variable) for sewage odours from a single works. Further correlations were achieved between the odour potential of a liquid sewage and the NOSE output of a quiescent sewage liquor. Hydrogen sulphide (H2S) concentrations, commonly used as measures of odour strength, were also compared with TON and found not to be a good marker compound for measuring these sewage odour concentrations. The results demonstrated the ability of an electronic nose to respond to sewage odours over a range of odour concentrations (125-781066 odour units/m(3)) and suggest the potential application of such an instrument to monitor odour emission;in a sewage works, as well as assessing the efficiency of odour abatement units. (C) 1998 Elsevier Science Ltd. All rights reserved.