Visual display terminals (VDTs) are in widespread and continuously increasing: use by a large number of people. Several physical factors may affect an operator's performance and health. These include visual factors such as display characteristics, image quality, resolution, stability, color, polarity, luminance, and contrast, as well as lighting conditions and indoor climate. Work station design and layout play the most critical role in eliminating sources of postural problems. Exposure of the operators to various radiations that may be produced by VDTs is not expected to have any health implications, as the levels of emissions are very low. Musculoskeletal effects and visual fatigue can usually be successfully controlled through proper design and use of work stations.