By using the standard arguments of covalency a simple theory has been developed for estimating spin transfer parameters in the linear bond
structure M 2+-F- -Cd2+ in crystals of CsCdF3:M2+,where M2+is Mn2+ or Ni2+ Data required are the experimental values of transferred and supertransferred hyperfine interations which were measured by ENDOR techniques. In this theory the measured isotropic supertransferred hyperfine interaction at cadmium site is assumed to be proportional to the unpaired spin fraction f?,in 2P?_orbita1 On fluorine ion. The results suggest that for Mn2+-F- bond f? =4.3% which is much larger than estimates from neutron scattering data though in reasonable agreement with recent work by Rinneberg & Shirley who used a method involving perturbed angular correlation of - rays from lllmCd.