Human activity is responsible for the entrance of toxic substances to aquatic ecosystems. These substances entail a risk for the components of the ecosystem (toxicological stress). Now, in addition, as a result of the global change, aquatic ecosystems are under strong environmental stress due to changes in water flow, light regime, temperature or nutrient concentration. Fluvial biofilms are attached communities consisting of bacteria, algae and fungi embedded within a polysaccharide matrix. In rivers, these communities are the first to interact with dissolved substances such as nutrients, organic matter, and toxicants. Fluvial biofilms, provide a community ecotoxicology perspective suitable for the assessment of acute and chronic effects of ecosystems' perturbations. Since species in a community differ in their range of tolerance to environmental and chemical stressors, it is expected that multi-stress situations of different magnitude and duration will cause structural and functional changes detectable at the community level. In this presentation, the assessment of ecosystem damage is addressed from a multi-biomarker perspective including functional and structural biomarkers measured in the fluvial biofilm. The main objective of this presentation is to update and illustrate the pros and contras of this multi-biomarker approach. Structural changes and functional responses of biofilm communities exposed to different organic (diuron, triclosan and b-bockers) and inorganic (Cu, Zn and Cd) toxic substances in experimental studies will be summarized and contrasted with the effects recorded in the field, under fairly uncontrolled multi-stress conditions. The advantages and limitations in the use of fluvial biofilms as multi-biomarkers of stress will be discussed.