BACKGROUND: Targeted ablation of anal canal highgrade dysplasia results in high recurrence over time. Circumferential radiofrequency ablation might decrease recurrence.OBJECTIVE: This study aimed to determine the safety and efficacy of circumferential radiofrequency ablation for anal high-grade dysplasia.DESIGN: This was a dual-center, prospective trial of circumferential radiofrequency ablation with a 1-year follow-up with longer follow-up data abstracted from medical records of study patients returning after trial for surveillance. Ten participants from the identically conducted pilot circumferential radiofrequency ablation trial were included to improve sample size for longerterm analysis.