Intra-abdominal and pelvic malignancies not infrequently are complicated by intestinal obstruction during their progressive course. How energetically this complication should be treated is a matter of controversy. An analysis of 41 such cases is presented. Small-bowel obstruction was most commonly caused by extensive serosal carcinomatosis, whereas obstruction of the large bowel usually was due to a single tumor. There was good concordance between the preoperative assessment of blockage level (small v. large bowel) and peroperative findings. All the patients with colonic obstruction obtained palliation from surgery, with median duration 6 months. Only 63% of the patients with small-bowel obstruction were relieved. This figure fell to 44%, with median duration of relief only 2 months, when carcinomatosis was the causal condition. The corresponding figures for patients with block caused by a single tumor were 89% and 6 months. Intestinal obstruction from non-malignant mechanisms was relieved in all cases. Surgical exploration should be attempted in these patients, as conservative measures are known to be of little benefit. In patients with extensive carcinomatosis, however, a favorable outcome in terms of symptom relief and prolonged survival is relatively unlikely.