We studied 123 patients having elective exploratory laparotomy through a midline vertical incision for gynecologic disease; patients were randomized to receive wound irrigation with either saline or topical thrombin before closure of the incision. Seven patients were not evaluable. No patient received low-dose heparin therapy perioperatively. No patient in either group had a clinically significant wound hematoma or disruption. Minor wound hematomas were more common in the saline group, a finding that approached statistical significance. Blood coagulation profiles were not different in the two groups either preoperatively or postoperatively. Topical thrombin is probably not clinically useful in preventing wound hematomas in patients who do not receive perioperative treatment with low-dose heparin; however, it seems to be safe for application to open wounds.