The publicity which has been given to Visual Display Terminals (VDTs) in recent years has been prompted by initial complaints from operators of visual and postural discomfort. The interest resulting from these complaints has led to much work being carried out on what appeared to be a potentially large problem. This work has precipitated recommendations and specifications from many quarters which in many cases are overcritical and rigid and do not take into account the great flexibility of the visual system and the need for mobility to maintain postural comfort. In this paper the VDT issue is considered with reference to: the known physiology of the visual and postural mechanisms; the psychological factors such as fatigue, boredom, stress and performance of operators; and the clinical aspects of ocular comfort.