[Endosonography in preoperative staging of gastrointestinal tumors]. 
29 patients with esophageal and gastric tumors, and 109 patients with rectal carcinoma were preoperatively investigated by endosonography.  Tumor infiltration and lymph node spreading were assessed by endosonography and compared to the postoperative histological findings.  Depth of tumor infiltration was assessed correctly in 88% of all patients investigated.  Lymph node spreading of gastric and esophageal cancer was detected in 84%.  In contrast lymph node metastases of rectal carcinoma were rarely seen.  The high accuracy of endosonography in detection of lymph node metastases of esophageal cancer makes it possible to select the appropriate treatment, such as surgery, radiotherapy or palliative procedures.  Endorectal sonography is a powerful tool to select those patients, who can only be treated by local excision.