The use of electricity to stun animals before slaughter was first developed in Germany and France in the 1920s. Electrical stunning systems are now used widely in the slaughter of pigs and sheep and, increasingly, for cattle. The Humane Slaughter Association (HSA), as part of its endeavours to promote high standards of welfare at slaughter has recently published an excellent set of guidance notes on the subject. This, the fourth in the HSA's ‘Guidance Notes’ series, describes the theory and practice of the use of electricity to stun and kill ‘red meat’ animals: cattle, sheep, pigs and goats (electrical stunning of poultry is not covered).