An epidemiological survey on 30,000VDT operators has been carried out to evaluate the relationship between asthenopia and monitor characteristics. A VDU operator has been classified as asthenopeic if he complained about at least two of the following ten symptoms: headache, tearing, eye smarting, blurred vision, double vision, ocular itching, photophobia, blinking, nausea, eye heaviness. Visual discomfort has been related to 1) the presence of flicker; the possibility to regulate, 2) brightness, 3) height; and 4) inclination of monitor. Asthenopia has resulted statistically correlated to the presence of flicker and to the impossibility of regulating height and inclination of monitor for both sexes. The possibility to regulate monitor brightness has not determined a reduction of visual discomfort either in men or in women.