Nuclear material accounting and control (NMAC) measures are designed to protect nuclear facilities and nuclear material from adversaries such as non-State actors both inside and outside the nuclear facility. This publication focuses on measures to prevent and mitigate the risk posed by insider threats. It describes elements of a programme that can be implemented at a nuclear facility in coordination with other systems existing at the facility level, such as operations, measurements and physical protection, for the purpose of deterring and detecting unauthorized removal of nuclear material.