This document provides an overview of orthodontic diagnosis. It defines diagnosis and introduces essential and supplemental diagnostic aids used in orthodontics. The essential aids include case history, clinical examination, study models, and certain radiographs. Supplemental aids require specialized equipment like cephalometric radiographs. Case history involves collecting patient details, chief complaint, medical/dental/family history. Clinical examination assesses the head, face, lips, nose, chin. Diagnosis aids in identifying the nature and cause of malocclusion to inform treatment planning.