We measured lead concentrations in samples of mineral salt mixtures used in cattle feed in the states of Paraná and São Paulo, Brazil. Lead content was determined spectrometrically by the atomic plasma induction method. Of the 30 samples analyzed, 9 had lead concentrations above 30 ppm (range 35.7 to 284.5 ppm) which is the maximum concentration recommended by the National Research Council (NRC 1980). These findings show the necessity for careful industrial monitoring because some mineral mixtures contain sufficient lead to cause toxicity.