Estudo preliminar sobre a hidroquímica da bacia de Jací-Paraná (RO)This study present the hydrochemical parameters of the streams of the Jaci-Paraná area. The samples were colected during October/84 to November/85, including dry an wet seasons. The parameters presented are pH, specific conductance, humic material, oxygen consumed, sulfate, calcium, manesium, sodium, potassium, chloride, iron, Kjeldahl nitrogen, silica. These waters are very poor in dissolved solids concentrations.