The absorption specva of ZnS:Ni and ZnSe:Ni were measured at 100 K under hydrostatic pressure up to 10 GPa. Two kinds of optical transition were investigated: (i) the d-d transifions between crystal field levels of Ni2+ in the tetmhedrd field of the host lattice and (ii) a charge transfer band that occurs when an electron is Vansferred from the valence band to the Niz+ ion. The pressure dependence of the crystal field parameter Dy and of the Racah panmeter B were determined and B revised assignment of the d d transitions was obtained. The charge tnnsfer c m be considered as a deep-acceptor tmsition. In this w e the Ni acceptor level may be used JS an energy reference. which enabled us to determine the hydrostatic deformation potentid of the valence band.