Zeolite A provides a unique opportunity to explore the relationship between structural parameters and 17 O nuclear magnetic resonance (NMR) isotropic chemical shifts ( δ ISO) because differences in site multiplicity for framework oxygens often permit unambiguous site assignments. Strontium exchanged zeolite A and hydrated and dehydrated K- and Na-A were investigated using 17 O triple quantum and five quantum magic angle spinning (3QMAS and 5QMAS) NMR. The results concur with previous observations that δ ISO is influenced by T–O–T bond angle, but also suggest that interactions between framework oxygens and extraframework species (water molecules and cations) affect δ ISO as well. Apparent chemical shifts for zeolitic water sites also exhibit relative chemical shifts as a function of extraframework cation contents consistent with shifts observed for water sites and non-bridging oxygens in glasses. Abundances of Si–O–Al sites in dehydrated forms indicate that oxygen isotope exchange rates can vary between crystallographic sites, as well as between Si–O–Si and Si–O–Al sites.