Zinc sorption was tested through four mineralogically diverse clay fractions of rendzina soils. The value and mechanisms of Zn sorption are strictly linked to the mineralogical composition of the clay fraction. Analysis of the variation of the buffer coefficient da/dCe, calculated according to the Freundlich isotherm, indicates that the fractions containing prevailing quantities of smectite, illite or kaolinite sorb Zn exchangeably (not specifically). Zn bonding in the smectite fraction is feeblest. The fraction containing opal CT adsorbs Zn permanently (specifically).