High-pressure 129 Xe NMR measurements were carried out on dehydrated (()-[Co(en) 3 ]Cl 3 to investigate the pore size as well as the local structure about the confined xenon atoms. At xenon gas pressures of 0.3 MPa, the xenon chemical shift was orientation dependent, exhibiting an axially symmetric powder pattern with δ 11 ) 280 ppm and δ 22 ) δ 33 ) 180 ppm. Proton to 129 Xe cross-polarization (CP) experiments selectively enhanced the portion of the powder pattern corresponding to δ 22 ) δ 33 ) δ ⊥ , confirming that the unique component of the chemical shift tensor, δ 11 ) δ | , lies along the pore axis. The isotropic chemical shift δ iso at the zero pressure limit was found to be 212 ppm, and suggested a pore diameter of approximately 0.47 nm. This agrees well with the diameter of 0.44 nm estimated from the crystal structure. On increasing the pressure to 6.5 MPa, δ ⊥ increased from 180 to 220 ppm, whereas δ | was found to be almost independent of pressure. The increase in δ ⊥ with pressure is attributed to Xe-Xe interactions. The paramagnetic shift in the xenon chemical tensor component perpendicular to the nanochannels with increasing pressure is in accord with the recent theoretical predictions of Jameson and de Dios (J.