Observations of electric field-gradient induced birefringence (the Buckingham effect) in gaseous N 2 over a range of temperature (~293-412 K) and pressure (up to ~2000 kPa) are reported. Analysis of the data shows that the temperature-independent contribution to the effect is not negligible, and values of the molecular hyperpolarizability, B, and quadrupole moment, Θ, are derived. In the case of the quadrupole moment, the experimental value [Θ=(-4.97+/-0.16)x10 - 4 0 Cm 2 ] and a state-of-the-art ab initio value [Θ=(-4.93+/-0.03)x10 - 4 0 Cm 2 ] due to Halkier, Coriani and Jorgensen [Chem. Phys. Lett. 294 (1998) 292] are in excellent agreement.