This paper describes synthetic routes to produce highly 17 O enriched samples of the negative thermal expansion materials ZrW 2 O 8 and ZrMo 2 O 8 . In the case of ZrW 2 O 8 enriched samples can be produced either via enriched Zr 17 O 2 and W 17 O 3 , which have themselves been characterised by both X-ray diffraction and solid state 17 O NMR, or via the hydrated material ZrW 2 O 8 ⋅xH 2 17 O. In the case of ZrMo 2 O 8 energy dispersive in-situ diffraction experiments have shown that cubic ZrMo 2 O 8 can be directly hydrated to form an enriched sample of ZrMo 2 O 7 (OH) 2 ⋅2H 2 O which can subsequently be transformed back to enriched cubic ZrMo 2 O 8 . 17 O NMR data of enriched ZrW 2 O 8 materials are reported.