High reliability electronic devices need to sustain thousands of electrostatic discharge (ESD) stresses during their lifetime. In this paper, it is demonstrated that repetitive ESD stresses on a protection device such as a bidirectional diode induce progressive defects into the silicon bulk. With “Sirtl etch” failure analysis technique, the defects could be localized quite precisely at the peripheral in/out junctions. The degradation mechanisms during repetitive IEC 61000-4-2 pulses have been investigated on a protection diode with the objective of improving the design for sustaining 1000 pulses at 10kV level.