Gonioscopy allows us to examine the angle of anterior chamber and forms part of complete ophthalmic examination and it is mandatory for the diagnosis and management of glaucoma. Gonioscopy permits the identification of eyes at risk for closure and detects angle abnormalities that could have diagnostic and therapeutic implications. Principle, types and techniques of gonioscopy, various types of gonioscopic lenses used, indications of performing gonioscopy, gonioscopic anatomy and grading are discussed in this article.