Odour bags from 10 sewage treatment works were used to assess the application of using an electronic nose to monitor sewage related odours. Canonical correlation (a data reduction technique) was used to compare the multivariate data generated by the NOSE (Neotronics Olfactory Sensing Equipment) with independent sensory panel analysis. Comparisons between the NOSE output and threshold odour numbers (TON) showed that no universal relationship exists between the NOSE and TON for sewage odours from a range of locations within different works. However, when similar groups of data from the same works (ie. biofilters) were compared, a linear relationship can be obtained between the NOSE output and corresponding TON values. Furthermore, this relationship could be extended to similar odours samples from different works, when only low TON values (ie. less than 4000 ou/m(3)) were analysed. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.