Salt marshes are brackish swamps formed in the estuaries of the rivers. The flora and vegetation of three marshes located at Puerto Saavedra (Cautín province, 38º 46' S and 73º 24' W), Mehuín (Valdivia province, 39º 26' S and 73º 12' W), and Quillaipe (Llanquihue province, 41º 32' S and 72º 44' W), distributed along 400 km in south-center Chile, were studied in 2000. Salt marshes are azonal plant formations independently of the macroclimate. A plant-sociological methodology was used to characterize these salt marshes. However, salt marshes studies should not differ in terms of floristic and vegetational characteristics. In each salt marsh, 10 sampling plots were equidistantly established along a 100-m-long transect beginning at the lower vegetation limit. Eighteen halophilic species were identified, and four were alochtonous: Cotula coronopifolia, Spergularia rubra, Leontodon saxatilis and Lolium multiflorum. The first specie was identified in the three salt marshes and it was the dominant specie in Mehuín. The other three species were detected only in Mehuín, suggesting that Mehuín was the most intervened place. The floristic similarity analysis demonstrated scarce affinity between marshes but, distant vegetation was more similar than closer one. Indeed, high affinity was detected between Mehuín and Quillaipe while low affinity was found between Puerto Saavedra and Quillaipe. These results were unexpected because Mehuín and Quillaipe were geographically more distant than Mehuín and Puerto Saavedra. According to the multivariate statistical analysis, flooding and salinity explained the altitutinal distribution pattern found for the plant species detected at each salt marsh. Floristic differences between salt marshes suggested the presence of a latitudinal gradient that contradicted the azonality condition described for salt marshes. These finding may be explained by differences in the coastal topography and it is also possible that differences in the substrate characteristics may existed along the latitudinal gradient.