This document discusses endoscopic sinus surgery (ESS) and the Messerklinger technique. It provides details on sinus anatomy and physiology, as well as factors that can lead to chronic sinusitis. Diagnostic nasal endoscopy is described as an accurate way to diagnose issues and determine appropriate treatment. True indications for ESS include chronic and recurrent acute sinusitis, nasal polyps, and fungal sinusitis. Advantages of ESS include a 3D view, good illumination, magnification, and the ability to visualize all areas of the sinuses. The conclusion states that ESS has clear advantages over conventional sinus surgeries in diagnosing and accurately treating patients.