Special Sessions on the Project STAR will be held parallel to other sessions (Convenor: Dr Mike T. Furse, Centre of Ecology and Hydrology, CEH Dorest B41, Winfrith Technology Centre, Winfrith Newburg, Dorchester, Dorest DT2 8ZD, UK). The EU-funded project STAR (Standardisation of River Classifications; EVK1-CT 2001-00089) provides scientific background for the implementation of the Water Framework Directive, in particular for biological monitoring systems. Based on many samples of benthic invertebrates, fish, diatoms and macrophytes, assessment systems were compared and intercalibrated, new methods were developed and CEN (Comité Européen de Normalisation) standardisation processes initiated. The STAR sessions with 14 oral presentations will give an overview of the main results of the project.