OBJECTIVE To evaluate the efficacy of transvaginal sonography and serum beta-hCG levels as diagnostic tools for deciding whether to perform operative laparoscopy in the treatment of presumed ectopic pregnancy (EP). DESIGN A prospective protocol for the evaluation and treatment of women with presumed EP. SETTING Department of Obstetrics and Gynecology, Haemek Medical Center, Afula, Israel. PATIENT(S) Eight hundred forty women with presumed EP who were seen in our emergency department from January 1988 through December 1995. INTERVENTION(S) On the basis of specific sonographic signs and beta-hCG levels, we performed immediate operative laparoscopy in patients with demonstrable extrauterine fetal heart activity or >100 mL of fluid in the pelvic cavity. We followed up all other patients, using defined criteria for laparoscopic intervention. MAIN OUTCOME MEASURE(S) The accuracy of transvaginal sonography in predicting EP was evaluated as part of the described protocol. RESULT(S) Overall, 380 patients were found to have EP. Of these, 331 were identified positively by transvaginal sonography and 49 were not. In 27 of 358 laparoscopies, no EP was found. The sensitivity of transvaginal sonography for the prediction of EP was 87% and the specificity was 94%. The positive and negative predictive values were 92.5% and 90%, respectively. CONCLUSION(S) In this protocol, which invariably captured the true location of the products of conception, using transvaginal sonography as the primary modality in the evaluation of patients with presumed EP resulted in the use of laparoscopy mainly as a treatment tool. This approach is both safe and economical.