Relativistic ab initio calculations of the 183W magnetic shielding constant and the chemical shift of WX 6(X = F and Cl) and WO 4 2− are presented. The computational method is a combination of the relativistic spin-free no-pair theory and the spin-orbit unrestricted Hartree-Fock method, which has been applied previously to 199Hg magnetic shielding constants. The spin-tree relativistic (SFR) terms, involving the mass velocity and Darwin terms, are shown to be important for 183W shielding constants. The spin-orbit interaction, which is smaller than the SFR term, works differently on WCl 6 and WO 4 2−. The effects of relaxing the inner s and p orbitals of W are investigated.