In many clinics, intraoperative sonography is used as a routine method in general surgery as well as in neurosurgery. The availability of sterilizable applicators in diverse shapes and sizes enables the optimal approach to the site to be examined. In processes involving the liver, the pancreas, the kidneys, or the brain, ultrasonic examination, together with an exact topographic localization, proved to be helpful in determining the dimensions of an altered structure. In patients with colorectal carcinoma, the discovery of metastases that had not been previously detected by percutaneous sonography proves the necessity of regular intraoperative ultrasonic examination to augment staging accuracy in tumor surgery.