The use of segmented mirrors for the primary elements of large telescope systems is becoming increasingly popular owing to the cost effectiveness of the design. Likewise, the use of non-optical flat glass in large collectors can further reduce cost. Unfortunately, both non-optical flatness and segment misalignment do result in phase errors. We have used a computer simulation to study the effects of these phase errors on the polarization state of an optical beam. We report herein on the effects of surface warping and of segment piston and tilt on the Stokes parameters of an optical beam reflected from a segmented mirror.