The X-ray findings were reviewed in 17 of 30 patients who had had advanced extrauterine pregnancy observed between 1946 and 1967. The presence of the following radiologic signs, either separately or in combination, were found to be diagnostically significant: abnormal fetal presentation and position, especially transverse lie with the fetal spine cephalad; failure to visualize the uterine shadow around the fetus; intermingling of the mother's intestinal gaseous shadows with the fetal parts; and, practically pathognomonic, fetal parts posterior to the mother's lumbar spine (lateral film). A hysterogram also demonstrates the uterine cavity as separate from the fetus, and occasionally there is visualization of a uterine mass separate from the fetus on soft-tissue X-ray study.