Atmospheric turbulence severely limits the resolution of groundbased astronomical telescopes. In good seeing conditions at the best observatory sites, resolution at visible wavelengths is typically limited to-1 s of arc. During the past 20 years adaptive optical systems using electrically deformable mirrors have been developed to compensate for turbulence effects. Unfortunately, these systems require bright reference sources adjacent to the object of interest and can be used only to observe the brightest stars. Artificial guide stars suitable for controlling an adaptive imaging system can be created in the upper atmosphere by using a laser to excite resonance backscattering in the mesospheric sodium layer. The design requirements of a laser-guided adaptive telescope, as well as the expected imaging performance, are reviewed in this paper.