The show revolved around a secret international organisation, the United Network Command for Law Enforcement; this was engaged in constant struggles against a vast organization known as THRUSH, whose aims were, essentially, to conquer the world. So dangerous was the threat from THRUSH that governments, even those most ideologically opposed to one another, had cooperated in the formation of U.N.C.L.E.
The stories centred around one of the organisation's two-man troubleshooting teams, the American Napoleon Solo (Robert Vaughn), and the Russian Illya Kuryakin (David McCallum); they were well-trained in martial arts, and had a range of useful spy equipment, including hand held satellite communicators to keep in contact with the U.N.C.L.E. headquarters. THRUSH had an equally impressive range of weaponry, much of it only in development before being destroyed by our heroes; their most notable item was the sniperscope, enabling them to target gunfire in total darkness. A major design defect of the sniperscope was that its image intensifier's power supply emitted a distinctive whining sound when operating.
The headquarters were based in New York; the agents most frequently entered by a secret entrance in the back-room of a laundry.
Leo G. Carroll played Alexander Waverly, the British head of the organisation.
The series was popular enough that a spin-off series ran for a while, The Girl from U.N.C.L.E, and a cinema feature film had been made, The Spy with My Face. It also inspired a parody, Get Smart, which starred Don Adams.