Skin ultrastructure was examined in patients undergoing CO2 laser resurfacing for facial rejuvenation. The lasers used in this study were the Coherent Ultrapulse CO2 laser with computerized pattern generator, the Sharplan Feathertouch laser, and the Laserscope Paragon-70 pulsed CO2 laser with computerized pattern generator. Results showed that the epidermis was totally removed with one pass of the CO2 laser. After one laser pass, there was little compaction of collagen in the dermis, but after two and three passes, there were sequential graded increases in collagen compaction with loss of the intervening extracellular gel matrix. There was no 'collagen shrinkage,' and the collagen itself was marginally affected, except for occasional losses in striations at the surface of the specimens. Elastin was very much affected by the laser such that with only one pass, the elastin was abnormal, presenting with a mottled heterogenous structure. This elastin aberrancy was present in both the papillary and reticular dermis. After one laser pass, fibroblast necrosis was present in the papillary dermis and the reticular dermis (depending on which laser was used), and the extent and depth of necrosis increased with multiple laser passes.