Video-endoscopic surgical treatment of the fetus may, in the future, become an alternative to open fetal operation. Six 95-day-old fetal lambs were examined through intrauterine endoscopy using amnioinfusion and specially designed balloon-tipped cannulas. The fetuses were monitored endoscopically for oxygen saturation, heart rate and temperature throughout the procedure. With a rigid 5 millimeter telescope and a flexible 3 millimeter endoscope, the respiratory and upper gastrointestinal tracts could be examined. No mucosal or other trauma was noted upon completion of the endoscopy; all lambs survived the procedure. While the applications of fetal endosurgery are likely to be similar to those of open fetal operation, fetal endoscopy (looking in the fetus) is a new entity for which clinical relevance (rather than mere feasibility) remains to be demonstrated. This technique, however, could become a valuable research tool to study fetal gastrointestinal and pulmonary physiologic factors in situ.