The purpose of this study is to determine the role of bleeding, acute thermal damage, and charring in adhesion formation. Postoperative adhesions were compared following ovarian wedge resection in 48 rabbits using different lasers, electrosurgery, and scalpel. Twelve ovaries were sectioned per modality, in randomized pairs. Acute thermal injury as assessed by histology, bleeding, and charring differed among the modalities used. Adhesions were assessed 4 weeks later, by an investigator completely blinded of the treatment protocol. The adhesion scores were 11.6 +/- 8.0 with pulsed Er:YAG laser; 11.9 +/- 7.5 with scalpel; 8.3 +/- 9.3 with electrocautery; 6.7 +/- 8.8 with a continuous (c.w.) Nd:YAG laser; 5.3 +/- 4.8 with c.w. CO2 laser; 3.1 +/- 2.7 with pulsed CO2 laser; 1.7 +/- 1.8 with pulsed Ho:YAG laser; and 0.8 +/- 1.5 in the control (no resection) group. Ho:YAG, Nd:YAG, and electrocautery were completely hemostatic. Bleeding was minimal with the CO2 lasers. Er:YAG and scalpel caused maximum bleeding, requiring hemostatic measures to prevent exsanguination. Charring occurred with electrocautery, CO2 laser, and Nd:YAG laser. Bleeding and charring correlated with adhesion formation, but the histological depth of thermal damage did not. The Ho:YAG laser is a hemostatic, fiber-optic compatible laser causing significantly fewer adhesions (P < 0.04) than scalpel, electrocautery, Nd:YAG, Er:YAG, and c.w. CO2 lasers. Clinical use of the Ho:YAG laser, and the role of carbonization in promoting adhesions, deserve further study.