EGSnrc is a general-purpose software toolkit that can be applied to build Monte Carlo simulations of coupled electron-photon transport, for particle energies ranging from 1 keV to 10 GeV. The included BEAMnrc component includes the dose scoring utility DOSXYZnrc to estimate radiation dose in a voxel geometry, such as patient medical imaging data. It also includes data processing tools to analyze the beam characteristic in detail and generate radiation dose profiles. EGSnrc is an extended and improved version of the EGS4 code system developed jointly by NRC and the Stanford Linear Accelerator Center in the 1980s (WR Nelson, H Hirayama, DWO Rogers. The EGS4 code system, Report SLAC-265, 1985). The EGSnrc implementation improves the accuracy and precision of the charged particle transport mechanics and the atomic scattering cross-section data (I Kawrakow. Accurate condensed history Monte Carlo simulation of electron transport. I. EGSnrc, the new EGS4 version. Medical physics 27, 2000). It also comprises a C++ geometry library for defining the geometry of complex simulation environments and particle sources. The BEAMnrc component is an improved version of the original BEAM package developed by NRC and the University of Wisconsin-Madison in the 1990s (DWO Rogers et al. BEAM: A Monte Carlo code to simulate radiotherapy treatment units. Medical physics 22, 1995).