Fate of heavy metals entered the soils is primarily controlled by interfacial reactions of the metals occurred on soil mineral surfaces. Soil is a complex environment containing various minerals and organic substances each of which can react differently with heavy metal ions. Therefore, it is a common approach to examine the interactions of metals with individual soil constituents in model systems for better understanding the role of every soil component in mobility and fate of metals in the environment. Free amino acids (FAA) are among the soluble low-molecular weight organic compounds. Amino acids can be obtained from a variety of sources such as wet and dry deposition, root exudates, dead roots and microbial and animal secretions. These organic compounds affect the mobility and sorption of heavy metals in soil. The e?ect of cysteine ??and histidine on the sorption of lead by palygorskite and sepiolite was investigated in a laboratory experiment. Sorption data were obtained at 0.01 M CaCl 2 and 0.5-2 mmol L -1 for lead in the presence of 1 mmol L -1 cysteine ??and histidine and described using Freundlich, Langmuir, Koble–Corrigan and Temkin models. The Freundlich and Koble–Corrigan models provided good fits for all sorption sets. Sorption of Pb by sepiolite and palygorskite was decreased in the presence of cysteine probably because of the formation of soluble complexes of Pb–cysteine in the solution. The complexes are stable and neutral-charged. Histidine effect was different for the two minerals. Sorption of Pb by palygorskite increased but that by sepiolite decreased in the presence of histidine. In the sepiolite-histidine system, very stable soluble ML 2 H + complex is the predominant form of Pb in solution. Formation of these complexes between lead and histidine may reduce the amount of lead absorbed by the sepiolite. In the palygorskite-histidine system, Pb mostly presents as ML 2 H 2 +2 and ML 2 H 3 +3 complexes which have a great desire to electrostatically sorbed by palygorskite. There is also a possibility of ternary surface complexes formation in this system. As a result, Pb sorption by palygorskite was increased in the presence of histidine. Sorption kinetics of Pb on both minerals was best ?tted to the power function equation both in the absence and presence of the cysteine and histidine. Rate of Pb sorption on sepiolite mainly decreased in the presence of cysteine and histidine. But in case of palygorskite, Pb sorption rate was decreased in the presence of cystein and increased in the presence of the histidine confirming the results of equilibrium studies. Keywords: sorption, amino acids, fibrous clay minerals, isotherm, ternary surface complexes.