From the outset of the development of the CANDU®1 reactor design, the reactor physics analysis of the core has relied on computer programs developed in Canada and international codes that have been modified and improved. Deterministic CANDU analysis is done in three stages: calculation of basic lattice properties, computation of the incremental effects of reactivity devices, and finally integration in finite-core calculations. Computer codes have evolved to account for the unique characteristics of CANDU reactors, such as the use of a cluster of fuel pins in rings, surrounded by a relatively large volume of heavy-water moderator, the three-dimensional arrangement of reactivity devices perpendicular to the fuel channels, and the on-power-refuelling feature of CANDU in channels with bi-directional coolant flow and bi-directional refuelling. The specific physics toolset methodologies that have evolved in the lattice code (WIMS-AECL), the reactivity-device code (DRAGON), and the finite-core code (RFSP) are reviewed. Examples of improved methods that have been developed more recently include, for instance, multi-cell capabilities in core-reflector interface models, transport calculations of the effect of interstitial reactivity devices, the time-average model for an equilibrium CANDU core and history-based local-parameter methods for snapshot core calculations. Coupled finite-core neutronic-thermalhydraulic calculations in models with very detailed three-dimensional coolant-density distributions have also evolved.