we developed a multimetric index that could discriminate natural from anthropogenic variability in 91 sites (63 reference sites and 28 disturbed sites) fairly evenly distributed across the upper grande river basin (bolivia). to do so, we examined 12 candidate metrics for their potential to indicate degradation and reflecting different aspects of macroinvertebrate assemblage structure and function. initially, using the reference sites, we developed statistical models describing the response of the different metrics to the natural environmental variability. in a second step, using sites experiencing three types of anthropogenic disturbances (i.e., agriculture, urban and mining activities), we quantified the deviation in the response of each metric model between reference and disturbed conditions. from the initial 12 metrics, we retained only 5 metrics in the final index (total richness, total abundance, richness of ephemeroptera, plecoptera and trichoptera (ept), percentage of ept abundance and percentage of scrapers abundance). these metrics were the most effective ones in responding to anthropogenic disturbances. our final index performed well in discriminating between reference and disturbed sites, giving a significant negative linear response to a gradient of physical and chemical anthropogenic disturbances. this index can be used as a monitoring tool to evaluate the biological integrity and aquatic biodiversity of the bolivian inter-andean valleys streams.