Cupping of the optic nerve head associated with normal intraocular pressure (IOP) is a common clinical presentation for which clearly defined management guidelines have not been established. The clinical approach represents a diagnostic challenge because the mechanism of optic nerve injury is often difficult to objectively establish. Of paramount importance is the primary distinction between physiologic cupping and pathologic cupping, and the accurate subclassification of eyes with pathologic cupping. Therefore, it is essential for clinicians to differentiate glaucomatous from nonglaucomatous disc damage. This article reviews the clinical differentiation of eyes with glaucomatous and nonglaucomatous optic disc cupping.