Experimental dynamic triggering characteristics of various SCR ESD protection circuits have been compared. These circuits include diode-chain-triggering SCR (Silicon Controlled Recitfier). low-voltage zener diode trigger SCR and gate-coupled low-voltage trigger SCR circuits. The magnitude of turn-on time, from the instant the SCR subjected to an electrostatic discharge (ESD) pulse to latch in a clamped state. strongly depends upon the type of ESD circuits. The temporal electrical response of the circuits to an ESD-like pulse in general can be divided into three regions: the delay region (I), the triggering region (II), and the holding region (III). Experimental results of diode-chain-triggering SCRs show that it is hard to distinguish phase I and phase II if the ESD overvoltage is high, however if the ESD overvoltage is slightly higher than the dynamic trigger voltage. then the above three regions can be clearly seen. This paper improves the understanding of the temporal development of ESD transient during the triggering process of SCR-type ESD protection circuits.