Abstract: This investigation was designed to integrate the quick-freeze technique for ion diffusion with two computer programs to permit the simultaneous measurement and calculation of the diffusivity of a variable number of ions in heteroionic soil system. Kaolinite clay was prepared so as to have the following percentage saturations of the CEC, Sr2+65, Mg2−15, Rb+10, Na+5 and H+5. A quadruplicate radioisotope tag consisting of 85Sr, 28Mg, 86Rb, and 22Na was used to measure the diffusivity of each ion. The complex spectra were resolved by use of Schonfeld's revised Alpha-M computer program. A probit-transformation procedure was formulated into a computer program to enable the calculation of each diffusion coefficient. These programs are described and illustrated with the diffusivity of 86Rb in kaolinite clay.