We studied the electric quadrupole interactions of Oxygen isotopes in a TiO2 single crystal. For l 30 and 19O nuclei, quadrupole coupling constants were measured by the β-NMR technique, and for the l70 nucleus the FT-NMR technique was utilized. We synthesized a TiO2 single crystal which was enriched in 170 up to 5 atom % to observe NMR signals without any perturbations from impurities. Using the known quadrupede moment of l7O, EFGs at an o site in TiO2 and the quadrupole moments of 13O and l9O were determined. © 1998, Verlag der Zeitschrift für Naturforschung. All rights reserved.