The search for a reliable means to detect deception has a long history. Because of the poor ability of most people, even professional ‘lie catchers’, to identify when someone is lying, a wide range of techniques have been developed to assist in lie detection. The link between physiological arousal and deception has been recognised for centuries, and in the nineteenth century scientists began to experiment with instruments that could measure this. The modern polygraph, which recorded changes in a number of physiological parameters, was developed in the early 1920s, with instruments designed to record changes in respiration, cardiovascular activity and sweat gland activity (forerunners to the modern polygraph) appearing in the 1930s. Since then the use of the polygraph as a ‘lie detector’ has been associated with controversy, with advocates and opponents exchanging blows often based on partial facts and full opinions. This article reviews the development of polygraphy, focusing on its emergence in the United States and to some extent in England, but also considers its role in newer applications, particularly sex offender treatment and supervision.