Despite certain improvements due to early diagnosis and the use of endoscopic tools, over 20% of large bowel malignancies still present themselves as an acute abdomen, most often with signs of bowel obstruction followed by perforation. A total of 949 patients have been operated for large bowel malignancies since 1984, of which 187 patients (19.7%) presented signs of bowel obstruction, including 35 (3.7%) that developed acute abdomen due to colonic perforation. Patients older than 60 were the most commonly affected of the whole group. The sigmoid colon was involved in 14 (40%) of the patients, the rectum in eight (22.8%) and the coecum in five (14.3%) of the patients. Early post operative mortality in patients that developed perforation was 28.5%. 5-year-survival rate was 12.5%.