Sulfur mustard has been used as a vesicant chemical warfare agent. To investigate the ocular damage it causes, we studied the effects on chemical casualties in the Iran-Iraq War. The patient population consisted of more than 5,000 chemical casualties, both military and civilian. The range of ocular damage was wide. The most common ocular effects were conjunctivitis and photophobia. Patients with significant corneal involvement are at risk for corneal ulceration and rarely for anterior chamber scarring and neovascularization, any of which would result in prolonged disability. In conclusion, the eye is the organ most sensitive to sulfur mustard vapor. Ocular injuries generally heal completely. In severe cases, blindness may occur. The need for corneal transplantation is rare.