Abstract The sorption behaviour of caesium in 19 different soils from various regions of Sweden and Libya was studied in batch experiments. All experiments were carried out in the presence of a supporting electrolyte (0.01 n CaCl 2). The experimental treatments were varying concentrations of Cs + from 0.03 to 0.767 meq/litre, and one level of K + and NH 4 +, 100 meq/litre. The sorption behaviour of caesium was complex. The distribution coefficient, the K d value, was strongly reduced after small additions of stable caesium. However, at increasing concentrations of stable caesium the effect became much less. Also, when potassium and ammonium were present in the experimental environment the caesium sorption capacity of the soils was reduced. It was also found that the clay content in the soils strongly influenced the sorption of caesium as shown by the K d values. Some of the Libyan soils showed higher K d values than the Swedish soils with similar clay content. The data available and the relationships found for the 19 soils were used in the development of simple mathematical models for prediction of transfer factors for caesium to wheat.