The purpose of this work was to study mineralogically the clay fraction of the Ibitiruna series (RANZANI e_t jal. 9). These soils belong to the Great Soil Group Red - Yellow Podzolic, Laras variety. Three profiles were collected within the areas where Ibitiruna series occur; these were labeled profiles P1, P2 and P3. The soil horizons were sampled individually in each profile from the surface down to the rock bed. The clay fraction was subdevided by centrifugation in coarce and fine clay with 0,2 micron as their limit of separation. The identification of clay minerals in the two fractions and a semiquantitative analysis was done by interpretation of the results obtained from chemical analysis (cation exchange capacity) and X-ray analysis (difratogram using a Geiger counter and films using the powder method). The mineralogical study of the two clay fractions, relative to the nature and quantity of clay minerals, indicate the following: kaolinita is the mineral that occur in greater quantit in the two clay fractions with a content always highter then 40%; the montmorilonite and the 14 A minerals normally occur values lower than 10%.