In January of 2006 we studied the distributional patterns of benthic macroinvertebrate communities of the Baker river basin (45 degrees 50' 0 and 47 degrees 55' S) and their main controlling factors trying to cover the greater variety of the lotic ecosystems. To carry out the study, 27 sampling stations were located in the different sub basins of the river. In each station, physical-chemical parameters of the column of water were quantified (conductivity, dissolved oxygen, pH, temperature and turbidity), and documented characteristics of the segment (e.g. wide of the channel and sediment type) and cartographic information using a geographic information system (GIS) and complemented with cartographic information using GIS. Identified a total of 5 1 taxa, are mostly insect larvae (80 %). The groups most richness were orders Ephemeroptera (15 taxa), Plecoptera (8 taxa) and Trichoptera (8 taxa). The classification and ordination analyses carried out with the data of abundance, allowed to recognize seven groups stations (A-F) statistically significant (P < 0.05). The multiple regression analysis, showed that the environmental variable that accounts for the observed biological patterns, was coverage cobble, explaining 45.1% the variance of the biological data (r(2) = 0.44 P < 0.05).