Five cases are described that involve severe attacks on humans by dogs who were being trained or maintained on an electronic pet containment system. The system is designed to boundary train a dog through the use of electric shock in an escape-avoidance conditioning paradigm. Data were collected from legal documents filed in personal injury lawsuits. Analysis of the findings show that all dogs lacked a marked history of aggressive responding, all were adult males, and most were reproductively intact. All attacks happened near the boundary of the property. In every case, the system was operational at the time of attack. Moreover, in most cases, the dog received shock. Findings lend themselves to possible interpretation in terms of unconditioned aggression as a result of a dog having received electronic shock and avoidance-motivated aggression mediated through fear reduction toward human stimuli.