This paper relates sesults obtained in the determination of available zinc by chemical and microbiological methods. The HCl 0,1 N, EDTA-(NH4) 2CO3, dithizone-ammonium acetate and Aspergillus niger (according WALLACE,1961 ) methods were applied to soil samples from profiles representing 8 soil series of Piracicaba Municipality, State of São Paulo, Brazil. The evaluation of the available zinc by the Aspergillus niger was splited in two parts: a- evaluation of available zinc in the samples soil from horizons of profiles of soils by microbiological method. b- Addition of crescent dosis of zinc (0 to 16 micrograms of zinc /0,25 g of soil) were made in the samples soil of upper horizons (Ap) of the profiles of soils.The special nutrientive solution without zinc and innoculum of Aspergillus were added to every treatment. After an week from inoculation to 28° C of temperature, the mycelium of Aspergillus was colected, dried to 70-80°C, weighed and registered the weights. Statistical correlations were conducted betwee the Aspergillus methods and every one of the chemical methods. Only the dithizone-ammonium acetate method showed correlation with the Aspergillus method. The results obtained by the Aspergillus niger method permited to classify the studied soils according the available zinc content, as follow low: Well suplied - Luiz de Queiroz Series Moderatly supplied - Bairrinho, Quebra-Dente and Lageadinho Series Low supplied - Iracema, Guamium and Paredão Vermelho Series.