Total bacterial counts, counts of Gram negative bacilli and faecal pollution were determined in samples of freshwater collected in different sampling sites of the fluvial system Itata, in the Eight Region of Chile. These stations cover the course of the system from the Andes down to the Pacific Ocean. Bacterial counts were rather low and varied according to the human population density in the sampling sites. Most of the identified bacilli were nonfermenting bacilli, among which the highest number were identified as Pseudomonas spp. Among fermenting bacilli, the highest proportion of strains corresponded to Enterobacter. In those areas with human activities faecal contamination indexes were higher and strains of aeromonas were isolated.