An analysis of the concentratlons of potassiurn, sodium. calcium. magnesiurn. tron, proteíns and fat, was made in the muscular tissue of the líned catftsh PseUliop laiystomajasciatLtm from the middle Orlnoco ínVenezuela, as a contribu tlon to the knowledge ofthe ecofisiology ofthe species and ofits importance from the nutritious point ofview. The salts were analyzed by Espectrofotometria ofAtomic AbsorpUon with fIame of air-acetylene and correction ofdeuterium bottom, using a tearn Perkin Elmer 3100 coupled with al1 automueslreador Perkin-Elmer ACE-51. The percentages of proteins and fa t were determined by the method ofWeede (Omcial Methods of Analysls,AOAC).An average 26,03 jo 5,08 pg/ g was determin d in tbe fron concentraUon. 387,05 jo 33,38pg/gin the concentration of calcium, 951,00 jo 236.04 pg/g In the concentraUon of magnesium, 1386,73 jo 47.39 pg/g in the concentration of sodiurn. and 11626.41 jo 365,23 pg/ g in the concentration of potassium. The average ín the concentratlon ofproteíns was of 18.1 jo 0,12% and that of fat 0.85 jo 0.03%.