The records of 66 consecutive patients who developed intestinal obstructions after treatment for cancer were reviewed. Approximately 1/3 of the patients had a benign cause of obstruction. The chances that an obstruction was due to cancer were increased if the patient had known metastatic cancer, previous colorectal cancer, if the primary was an advanced stage, and if the interval since treatment of the primary was short. Incomplete obstructions were treated with nasogastric suction. Although resolution of the obstruction on nasogastric suction without operation occurred in 24% of the admissions, 41% of those patients had to be readmitted for surgical relief of recurrent intestinal obstruction. Resolution of an obstruction on nasogastric suction occurred early, and there was little point in continuing a trial of suction for longer than 3 days.