ABSTRACT The purpose of this case series is to review the endoscopic detection of anal intraepithelial neoplasia and anal squamous cell carcinoma including the role of rectal retroflexion and narrow-band imaging. Four cases of anal intraepithelial neoplasia were incidentally discovered in women aged 55–71 years. Anal lesions identified included sessile polyps, nodular mucosa, and circumferential polyps. A fifth patient, who presented with abdominal pain, was found to have a 3 cm anal squamous cell carcinoma on diagnostic colonoscopy, despite a negative colonoscopy 21 months earlier. In the absence of contraindications, retroflexion should be performed on all patients. Suspicious anal mucosa warrants biopsy.