A sudy was made regarding the influence of salinity on the distribution of Egeria densa in the Valdivia river basin, Chile. Measurements were taken of the biomass of this species from locations of differing salinity within the range of its distribution in the Valdivia river. In the laboratory, the growth and photosynthetic rates of shoots kept in different saline concentrations were recorded. It was found that Egeria densa tolerates salinities up to 5g/l, which grow naturally in the Valdivia river. In the laboratory, by contrast, it prospers in concentrations up to around 8g/l. In concentrations up to around 1 g/l there is a clear stimulation of shoots growth; in greater concentrations a slight inhibition of photosynthesis, growth and adventitious roots production is noted.