We present an analysis of the complex of water with N-2 which includes (a) ab initio calculations of the potential energy surface; (b) ab initio analysis of the different contributions to the interaction energy (exchange, electrostatic, dispersion, induction); (c) a diffusion Monte Carlo study of the vibrational ground state and a calculation of vibrationally averaged spectroscopic constants for the different isotopic species; (d) construction of an N-2..H2O potential function by fitting to ab initio points followed by adjustment against the experimental rotational and quadrupole coupling constants of Leung et al. [J. Chem. Phys. 90, 700 (1989)].