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The EPR g factors g(x), g(y) and g(z) and the local structures for the orthorhombic Nd3+ centers in YAG, YGG and LuGG garnets are studied by using the perturbation formulas of the g factors for a 43 ion in orthorhombic symmetry. In these formulas, the contributions to the g factors arising from the second-order perturbation terms and the admixture of various energy levels are considered. Based on the analyses of the g factors, we find that the polar angles theta'(j) of the impurity-ligand bonds related to the Z-axis of the crystals in these Nd3+ centers are smaller than the host angles theta(j) in pure crystals, whereas the azimuthal angles phi'(j) related to the X-axis in the impurity centers are larger than the corresponding phi(j) in the hosts. The calculated g factors, particularly their anisotropies Delta g [= g(z) - (g(x) + g(y))/2] and delta g (= g(x) - g(y)) for Nd3+ in the gamets based on the above local angles show reasonable agreement with the observed values. (c) 2004 Elsevier B.V. All rights reserved.