We have precisely measured O-17 longitudinal relaxation times, T-1(O-17), of CO2 under gaseous, liquid, and supercritical conditions at four different temperatures of 293.4, 313.0, 331.8, and 351.4 K over a wide pressure range between 1 and 20 MPa, corresponding to a density range between 0.03 and 0.94 g cm(-3). Assuming that the quadrupolar interaction is a dominant mechanism in the O-17 relaxation, the reorientational correlation time, tau(2r), of CO2 was obtained from T-1(O-17) with a known value of the quadrupole coupling constant. The tau(2r) in CO2 thus determined showed a unique density dependence; tau(2r) decreased rapidly with increasing density at lower densities up to similar to0.2 g cm(-3), tau(2r) seemed to be insensitive at intermediate densities between 0.2 and 0.6 cm(-3), and tau(2r) moderately increased at higher densities more than 0.6 g cm(-3). It was demonstrated that the density dependence of tau(2r) in CO2 has a clear minimum near the critical density. The present experimental results of tau(2r) perfectly agreed with the calculation ones recently reported by Adams and Siavosh-Haghighi (J. Phys. Chem. B 2002, 106, 7973). The rotational dynamics of CO2 was discussed over a wide range of density and temperature in terms of tau(2r) together with the angular momentum correlation time.