Endorectal ultrasound examination is a valuable method for detection and monitoring of pelvic diseases. The authors record their clinical experience in endorectal ultrasonography with Bruel & Kjaer ultrasound scanner. One hundred patients with diseases of the pelvic organs were examined, mainly before and after operation of ano-rectal cancer. There were 59 patients with rectal cancer, 8 patients with relapse after rectal resection, 3 patients with anal cancer, 2 patients with insufficiency of the anastomoses after rectal resection with formation of pelvic abscesses, 2 patients with metastases of bladder cancer, 2 patients with rectal cancer invading the prostate gland, 1 patient with vaginal cancer invading the rectum, 1 patient with rectal cancer invading the bladder and both ureters leading to bilateral hydronephrosis and 2 patients with extrauterine pregnancy. Another group of 20 patients was examined for detecting early postoperative recurrences. EU is an obligatory method of diagnosis of rectal cancer. It is part of the complex approach to the choice of operative method and helps to make short- and long-term prognosis after the operation. The method is also essential for the diagnosis of inflammatory processes in the pelvis and in-lying organs.