It is anticipated that head tracked 3D displays will provide the next generation of display suitable for widespread use. Although there is an extensive range of 3D display types currently available, head tracked displays have the advantage that they present the minimum amount of image information necessary for the perception of 3D. The advantages and disadvantages of the various 3D approaches are considered and a single and a multi-user head tracked display are described. Future work based on the findings of a prototype multi-user display that has been constructed is considered.