To assess sonographic findings in the evaluation for ectopic pregnancy, all women referred over a two-year period were prospectively evaluated. The incidence of intrauterine as well as adnexal findings was assessed in an attempt to optimize sonographic evaluation. Visualization of a double decidual sac sign (DDSS) within the uterus provided an accurate means of confirming an intrauterine pregnancy (IUP) prior to embryo visualization. Forty-two of 130 women with IUP were diagnosable only by the DDSS. As a screening test for ectopic pregnancy, sonographic documentation of an IUP provided the only convincing evidence for the absence of an ectopic gestation. Any woman clinically at risk for ectopic pregnancy whose sonogram did not confirm the presence of an intrauterine pregnancy was at relatively high risk (43 per cent) for having an ectopic gestation. Characterization of adnexal findings increased the level of risk for ectopic pregnancy in these women to 70-100 per cent. However, 20 per cent of women with a surgically confirmed ectopic pregnancy had normal adnexal findings.