The electron paramagnetic resonance spectrum of trigonal Fe3+ centres has been investigated and parameters of the spin Hamiltonian obtained for nominally pure congruent LiTaO3 crystals annealed at ∼1500 K under Li2O vapour pressure corresponding to the pressure over the stoichiometric lithium tantalate. The possibility of calculating the zero-field splitting of the ground state of the impurity ion on the basis of the superposition model is discussed.