The benefits and the costs of three-dimensional displays are first discussed. Then the different depth cues which are used to perceive depth are reviewed and the conclusions of psychological studies which have examined these cues in combination are reported. These conclusions generally support an additive linear model of depth perception with heavy weighting given to binocular disparity, motion parallax, and interposition. However, the presence of motion sometimes reduces the salience of disparity. Techniques for implementing both stereoscopic and perspective displays are then reviewed in detail.