Abstract Purpose: To determine whether ocular hypertension (OHT) is over diagnosed in patients with increased corneal thickness. Methods: Thirty-six patients with OHT were compared with 29 control subjects and 31 patients with glaucoma. Corneal thickness was determined by ultrasonic pachymetry and measured at a single point, 1.5 mm temporal to the corneal light reflex. Results: The corneal thickness (mean ± standard deviation) in patients with OHT was 0.610 ± 0.033 mm. This was significantly greater than in patients with glaucoma (0.557 ± 0.039 mm) and control subjects (0.567 ± 0.036 mm). Conclusion: It is well documented that increased corneal thickness leads to artificially high estimations of intraocular pressure. This study confirms that a significant number of patients with OHT have a normal intraocular pressure if corneal thickness is taken into account. Corneal pachymetry is clinically helpful in estimating intraocular pressure, determining the risk of visual loss, and establishing a target pressure.