Background-In patients with implantable cardioverter-defibrillators (ICDs). inappropriate shocks have been reported with exposure to electronic article surveillance systems. The risk to patients with ICDs of walking through or lingering near surveillance systems requires further investigation. Methods and Results-We evaluated the response in ICD function in 170 subjects during a 10-to 15-second midgate walk-through of and during extreme (2 minutes within 6 in of the gate) exposure to 3 common article surveillance systems. Complete testing was done in 169 subjects. During a 10-to 15-second (very slow) walk-through of the 3 surveillance systems, no interactions were observed that would negatively affect ICD function. During extreme exposure (169 subjects) and during extreme exposure and pacing via the ICD (126 subjects), interactions between the ICD and the article surveillance systems were observed in 19 subjects. In 7 subjects, this interaction was clinically relevant and would have likely (3 subjects) and possibly (4 subjects) resulted in ICD shocks. In 12 subjects, the interaction was minor. Conclusions-It is safe for a patient with an ICD to walk through electronic article surveillance systems. Lingering in a surveillance system may result in an inappropriate ICD shock. (Circulation. 1999;100:387-392.)