The potassium titanyl phosphate (KTP) and argon lasers are increasingly used in nasal and sinus surgery. Histologic effects of these lasers on living nasal tissue have not been investigated. Sixteen dogs underwent laser nasal surgery (eight for each laser). Flexible fiberoptic quartz fibers were used with both lasers to deliver the laser energy to the tissue. The dogs were allowed to heal and then underwent biopsy at 3, 7, 21, and 90 days postoperatively. The argon and KTP lasers had similar tissue effects. Histologically, a thin rim of coagulation necrosis and acute inflammation were seen at 3 days postoperatively. By 7 days, fibroblasts and granulation tissue were observed. At 21 days, fibroblast proliferation and re-epithelialization with respiratory epithelium were the predominant findings. Finally, at 90 days postoperatively, respiratory epithelium and submucosal structures were found overlying a plug of scar filling the defect in the septal cartilage. This healing was consistent through a wide range of energy densities. These lasers are easily used with sinus endoscopes and the operating microscope to allow access to difficult areas. These factors and the wound-healing characteristics noted in this study would seem to make them suited for use in rhinologic surgery.