The configuration interaction between the t24 and t23e configurations has been taken into account to calculate the energy levels of the (OsCl6)2- complex ion in the intermediate-coupling scheme. The matrix elements of the magnetic moment operator between the ground level A1 and the excited T1 levels are given in algebraic form, and then used to calculate the temperature-independent paramagnetic susceptibility. The experimental value of the susceptibility and a part of the optical absorption spectrum can be fitted to theory by choosing the following values of the parameters: B=365. 5 cm-1, C=1561. 0 cm-1, ?5d=2575. 0 cm-1, ?=33 000. 0 cm-1, k=0. 7, k'=0. 7. © 1971 The American Physical Society.