Extended X-ray absorption fine structure (EXAFS) spectroscopy has been used to characterise polyoxometalates of the type M_mO_y^n– and X_xM_mO_y^n– in the solid state and in solution. The best fit to the low-temperature (80 K) niobium K-edge EXAFS of K₇[HNb₆O₁₉]·13H₂O was obtained with one terminal oxygen at 1.79 Å(M–O_t), four doubly bridging oxygens at 1.97 Å(M–O_b), four niobiums at 3.32 Å and one niobium at 4.76 Å. The Nb–O_b–Nb bond angle was determined as 113° following a multiple-scattering calculation for this unit. Analysis of the niobium K- and tungsten L_III-edge EXAFS of salts of Nb_xW_{6 –x}O₁₉^{(x+ 2)–}(x= 2–4) yielded Nb–O bond lengths of 1.74–1.76 and 1.98–1.99 Å, W–O bond lengths of 1.72–1.74 and 1.89–1.91 Å, and non-bonded M ⋯ M distances of 3.31–3.35 and 4.74–4.78 Å. The first co-ordination spheres also comprise one six-fold bridging oxygen at about 2.3 Å but this shell is poorly defined due to static and thermal disorder in the bond. A combination of vanadium K- and tungsten L_III-edge EXAFS of [V₂W₄O₁₉]^4– yielded W ⋯ W separations of 3.27 Å but shorter V ⋯ W separations of 3.20 Å, showing a slight distortion in the hexametalate structure that is not observed for the niobotungstates. Molybdenum K-edge EXAFS analysis of [NBuⁿ₄]₃[PMo₁₂O₄₀] in the solid state at 80 K revealed systematic asymmetry in the Mo–O_b bonds with two oxygens at 1.81 and two at 1.97 Å. The structure is not perturbed when the salt is dissolved in acetonitrile. Likewise the molybdenum K-edge EXAFS of [TeMo₆O₂₄]^6– in water and [Mo₆O₁₉]^2– in acetonitrile analysed for the same co-ordination spheres as those of the parent salts Na₃[TeMo₆O₂₄]·nH₂O and [NBuⁿ₄]₂[Mo₆O₁₉].