Local cancer recurrence may occur at the suture line in the intestine after removal of gastrointestinal tumors, in the pleural or peritoneal cavities, or in operative incisions. The most frequent cause of recurrence in operative wounds is a microscopic extension of the tumor left at the operative site; it is probably not often the result of contamination of the surface of the tissues with cancer cells following incision into the tumor or taking a biopsy. A solution containing a cytotoxic chemical has been used to irrigate the operative site; this will affect cells on the surface but will not penetrate residual malignant processes. Injection of a chemical into the systemic circulation or an artery supplying the region will cause greater effect. Ionizing radiation, however, will act more uniformly on the tissues and the dose can be accurately controlled. The water content, electrolytes, and deoxyribonucleic acid in the cancer cell are