Unlabelled - For patients at high risk of anal cancer, annual screening strategies using invasive evaluation methods are stressful. According to a normal examination at baseline using simple and non invasive tests, the aim of the work was to quantify neoplastic events. Patients and method - Data from patients with a normal evaluation at the first visit were retrospectively extracted from a prospective database. The individual follow-up period was at least two years and three evaluations. Patients with abnormal cytology were assessed using high-resolution anoscopy and targeted biopsies. Results - A total of 182 subjects (F/M: 10/90, aged 48.1(10.6) years, HIV: 81%) were followed for 41(11) months. Anal cytology remained normal in 94 patients (52%), but high-grade anal neoplasms occurred in 28 patients (15%). Patients with a negative HPV16 status at baseline had cumulative probabilities of high-grade AIN of 0.4%(0.1%-1.9%), 2.6%(1.2%-5.9%) and 7.5%(4.5%-12.2%) after 1 year, 2 years and 3 years of follow-up, respectively. These probabilities were lower than those of patients with a positive HPV16 at baseline and those with a previous history of AIN. Conclusion - In patients with normal cytology and negative HPV16 at baseline, a three-year interval screening may be a less cumbersome alternative to traditional annual screening.