Objective To investigate the clinical significance of endorectal ultrasonography (EUS) to rectal cancer. Methods To compare 38 cases of rectal cancer with EUS to their pathology after surgery from May 1995 to August 1998.Results 2 cases were not found by EUS because of their distances to the anus over 12. 0cm. The other 36 cases of rectal cancer were detected by EUS:among them the depth of invasion of 7 cases were muscularis mucosae and submucosa in EUS

while 8 cases in pathology; the depth of invasion to muscularis propria

there were 17 cases in EUS while 15 cases in pathology;so to serosa

there were 12 cases in EUS

while 15 cases in pathology; the total rate of accurate diagnosis of EUS was 83% (P>0.05)

the accuracy of EUS in detecting regional lymph nodes metastases was 62% (18/27) (P>0.05)

the other organs invaded in EUS were 7 cases

while in pathology were 8 cases. Conclusion EUS can show the depth of invasion

metastasis of lymph nodes and other organ damage in rectal cancer before operation

it has important value for the mode of surgical treatment.