From 1 July 1990 to 31 January 1994, 55 patients underwent operative laparoscopy for the excision of monolateral endometriomas. None of the patients had previously undergone surgery by laparotomy or laparoscopy. At the time of laparoscopy, the surgeon staged the disease according to the American Fertility Society classification of endometriosis. A second surgeon, blinded to the preoperative management of the patients, re-staged the disease based on a videotape review. Interobserver disagreement was between 0 and 12%. Total, endometriosis (deep and superficial) and adhesion scores were evaluated separately. These scores in patients who had previously undergone transvaginal ultrasound-guided aspiration of the cyst content (n = 13) were compared with those from patients who had not undergone this procedure (n = 42). The total and endometriosis scores were not significantly different between the two groups, whereas the adhesion score in patients who had undergone a transvaginal aspiration procedure was significantly higher than in patients who had not (mean +/- SD, 12.0 +/- 13.7 versus 5.9 +/- 4.6; P = 0.02). Therefore it is possible that transvaginal ultrasound-guided endometrioma aspiration may determine tissue trauma that enhances adhesion formation.