Purpose of Review <p>The purpose of this review is to provide gastroenterologists a basic understanding of what anal squamous intraepithelial lesions (ASILs) are, how they develop, who are the high-risk populations, who and how to screen, and management of these lesions.</p> Recent Findings <p>Human papilloma virus (HPV) infection is the most common cause of squamous cell carcinoma of the anus. Anal intraepithelial neoplasia is a precursor to the development of anal squamous cell carcinoma, and screening can lead to early detection and cure. Despite the availability of HPV vaccination for primary prevention, the mortality from squamous cell carcinoma of the anus continues to rise.</p> Summary <p>ASILs are precursor lesions to anal cancer, and with proper detection and treatment, the risk of anal cancer progression can be lessened. We discuss the screening and surveillance of these lesions, and their further management when high-grade dysplasia or cancer develops.</p>