INTRODUCTION: Diagnostic accuracy of first-line sonographic evaluation by obstetrics/gynecology residents in determining the need for emergency surgery in women with acute pelvic pain is unknown. Aim of this study was to evaluate the diagnostic accuracy of routine ultrasound evaluation by obstetrics/gynecology residents, available 24 hours a day, in patients with acute pelvic pain. METHODS: A cross-sectional retrospective study included consecutive patients who underwent emergency laparoscopy for acute pelvic pain at a teaching hospital gynecologic emergency unit, between January 1, 2004, and December 31, 2006. The laparoscopic diagnosis was the reference standard. Gynecologic and nongynecologic conditions requiring immediate surgery to avoid severe morbidity or death were defined as surgical emergencies. In all patients, obstetrics/gynecology residents routinely performed clinical examination and standardized ultrasonography was routinely recorded. Sonograms were re-interpreted for the study, blinded to physical examination and laparoscopic findings, according to evidence-based predetermined criteria. Sensitivity, specificity, and likelihood ratios were computed for clinical data alone, sonographic data alone, and the combination of both. RESULTS: Emergency laparoscopy was performed in 234 patients, diagnosing 139 (59%) surgical emergencies. Clinical and sonographic examinations performed by the residents each independently predicted a need for emergency surgery. Combining both examinations was superior over each examination alone and had an acceptable false-negative rate of 1%. CONCLUSIONS: First-line combined clinical and sonographic examination by obstetrics/gynecology residents is effective in ruling out surgical emergencies in patients with acute pelvic pain.