The conceptual design of the Gran Telescopio Canarias (GTC) has been completed. One of the challenges facing the GTC Project is to obtain excellent image quality using a segmented primary mirror. The segmentation will introduce a physical effect that contributes to significant degradation of image quality. The image quality requirement imposes the use of an active optical system to correct figure instabilities of the optical surfaces and part of the unavoidable fabrication figure errors. The active correlation includes the capability of 5-axis motion of the secondary mirror, 3-axis motion of each primary mirror segment, and 6 active degrees of freedom to deform each segment. A mixed strategy of closed- and open-loop control of the active correction will be implemented. This paper discusses the expected wavefront errors of the GTC, how they are corrected by active optics, and the expected image quality performance in FWHM, (theta) 80 and Central Intensity ratio.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.