Fifty-seven of 261 patients (21.8%) referred with a presumptive diagnosis of an ectopic gestation had an extrauterine pregnancy. Five of the 57 ectopic pregnancies (8.8%) had a pseudogestational sac on transvaginal sonography. In four of these five cases, a single beta-hCG level had been obtained and did not help in differentiating an ectopic gestation from an early intrauterine pregnancy. A thorough assessment of the adnexa and cul-de-sac should be performed if a patient suspected of having an ectopic pregnancy has an apparent intrauterine gestational sac without a normal yolk sac or without detectable fetal cardiac activity.