Nanocrystalline MgO has been sol-gel manufactured to give a range of crystallite sizes from 1.8 to 35 nm as determined by powder X-ray diffraction. A multinuclear magnetic resonance approach using 13 C, 17 O, and 25 Mg provides information on the atomic scale structure. It is found that despite extensive hydrolysis that -CH 3 fragments persist until extensive calcination has been performed. In 17 O magic angle spinning NMR spectra three signals are detected that are assigned to MgO-like, a surface species, and a unit also like MgO but with carbon as the third nearest neighbor, demonstrating the high sensitivity of the 17 O chemical shift to local structure and its ability to detect medium-range order.