Existing data from field surveys have been reanalysed in order to establish relationships between odour annoyance and odour exposure concentrations caused by (bio) industrial odours in a community. The percentage of highly annoyed persons (%HA) was found to have a simple relationship with the logarithm of the 98 percentile of the odour exposure concentrations (lgC98). Pleasantness ratings of the odours were obtained through a supplementary laboratory study with samples from the sources concerned. It was found that the prediction of %HA improves if the pleasantness of the odour is taken into account. The %HA at a certain level of lgC98 is found to be higher when the odour is less pleasant. This indicates that odour standards may improve if they take the odour pleasantness into account. Before doing so the possibility must be ruled out that the effect of pleasantnees on %HA was caused by factors confounded with the pleasantness of odours. Copyright (C) 2000 Elsevier Science Ltd.