Advanced nodal methods for the solution of the multigroup neutron diffusion and transport theory equations in three-dimensional hexagonal-z geometry are described. The code HEXNOD allows an accurate and efficient calculation of three-dimensional problems for fast reactors and high converter light water reactors. A unique capability of HEXNOD is the accurate solution of global three-dimensional neutron transport problems for fast reactors with very small computing times. The accuracy of the nodal diffusion and transport approximations is demonstrated by comparison with conventional finite difference methods and Monte Carlo calculations for a number of mathematical benchmark problems. Based on numerical results, it is concluded that the code HEXNOD is well suited for three-dimensional routine analysis of fast reactors and, in particular, as the neutronics module of the generalized quasi-static kinetics program HEXNODYN, which is currently being developed as part of the European accident code EAC-2.