An ESD protection circuit and device structure comprises five transistors, two PNP and three NPN. The five transistors are coupled together so that a first NPN and PNP pair constitute a first silicon controlled rectifier, SCR. The NPN transistor 102 of the first SCR and a third transistor of NPN type are coupled so that they constitute a Darlington pair. A further NPN and PNP pair are coupled together to form a second SCR with the collector of the PNP transistor of the first SCR being coupled with the emitter of the PNP transistor of the second SCR. The circuit is particularly suitable for high voltage triggering applications and two or more devices may be cascaded in series in order to further increase the triggering voltage.