RESUMEN
Total mercury concentrations were measured bimonthly between April 1994 and February 1995. Samples were made in three subsystems of the Paraná river's floodplain, between Paraná and Mato Grosso do Sul States, Brazil. The total mercury content was determined by H2SO4/KMnO4 digestion, SnCl2 reduction, and vapour generation method analysis (CGCH900), adapted to Atomic Absorption Spectrometer (CGAA 7000 ABC). Mean mercury concentration in composite water varied from .64 to .78 ng.ml-1 in these subsystems. Potassium explained 59 per cent of the variability of water mercury in Paraná/Cortado, while pH explained 20 per cent and maximum depth explained 37 per cent in Baia/Guaraná and in Ivinhema/Patos, respectively. Some mercury values in April and August exceed criteria for issuance of water consumption advisories (>.002 ug.ml-1)