To determine the value of transvaginal sonography in the evaluation of women with suspected ectopic pregnancy, we retrospectively studied 47 pregnant patients in whom both conventional transabdominal sonography (TAS) and transvaginal sonography (TVS) had been performed. Each patient had been given a standard TAS examination with the bladder moderately distended. After voiding, a TVS examination was performed. TAS and TVS were compared for their ability to reveal specific sonographic findings, including the double decidual sac sign, yolk sac, embryonic pole, and embryonic heart activity. Results indicate that the important sonographic findings of early pregnancy are more likely to be seen transvaginally than transabdominally. In 23% of the patients, only TVS provided the findings for diagnosis of the location and status of the pregnancy. In another 22%, the information gathered through TVS allowed increased confidence in the diagnostic accuracy of the TAS findings by providing additional findings. Therefore, in 45% of the cases, TVS influenced clinical decision-making. In no case was TVS less informative than TAS. These results support the claim that TVS contributes to diagnostic accuracy in early pregnancy. TVS should usually be used in conjunction with, and not as a substitute for, TAS. TVS is best used when TAS is not conclusive, or when immediate confirmation of an intrauterine pregnancy is desired.