Determinations of Mo, Co, Cu, Zn, Mn, and Fe soluble in hot 6N HC1 were carried out on 31 limestones and 2 siderurgy slags employed in the neutralisation of soil acidity in the State of São Paulo. In the limestones, the average, minimum and maximum contents of Mo, Co, Cu, Zn, Mn and Fe, expressed in ppm were: 0.9(0.1-5.0); 4.2(0-46.9); 11.0(5.4-42.2); 15.2(7.5-46.0); 810(30-1760) and 3905(159-33,110). In the two analysed siderurgy slags samples the contents obtained were: Mo 2.5 and 5.3 ppm; Co 2.6 and 11.4 ppm; Cu 2025 and 7800 ppm; Zn 750 and 1250 ppm; Mn 8100 and 38,600 ppm and Fe 4522 and 127,150 ppm.