Objective To investigate the long-term incidence of in-stent stenosis(ISS)in patients with intracranial aneurysms receiving pipeline embolization device(PED)who showed no ISS at short-to-medium term follow-up examination.Methods The clinical data of patients,who received PED treatment at the Department of Neurointervention,First Affiliated Hospital of Zhengzhou University of China between April 2015 and June 2022,were retrospectively collected.The patients with intracranial aneurysms,who showed no ISS at the initial follow-up with DS A and completed>12 months long-term follow-up check after treatment at the same hospital,were screened out,and their relevant clinical data and imaging materials were collected.The incidence of ISS occurring in postoperative>12 months long-term follow-up was calculated.The ISS was defined as a>25%lumen loss of the parent artery when compared with its lumen size measured immediately after PED implantation.Results A total of 57 patients with 61 aneurysms were enrolled in this study,and a total of 68 PEDs were implanted.Forty-one(67.21%)aneurysms were treated by PED implantation only,and 20(32.79%)aneurysms by PED plus spring coils.The median initial follow-up time was 184.0 days(119.0,212.5).At postoperative>12 months long-term follow-up visit,DSA was employed for 35(57.38%)aneurysms,CTA was adopted for 22(36.07%)aneurysms,and 3D-SPACE sequence MR scan was performed in 4(6.56%)aneurysms.The median follow-up time was 538.0 days(407.5,678.0),and the incidence of ISS was 0%.No ISS-related neurological symptoms occurred in all patients.Conclusion In treating intracranial aneurysms with PED,the postoperative incidence of ISS is low.No ISS is found during the short-term follow-up period,and long-term follow-up results tend to indicate that no ISS events have occurred.