Background: Acute obstruction of the colon continues to be a lethal disease with little improvement in the mortality rate over the past 50 years. So, this study was undertaken to define the causes of colon obstruction and their probable changes after years. Methods: From 1979 to 2004, all records of patients with definite diagnosis of intestinal obstruction at all hospitals affiliated to Shiraz University of Medical Sciences in Shiraz, southern Iran were reviewed retrospectively. Results: One thousand-hundred and seventy-two patients with diagnosis of intestinal obstruction entered our study. Two-hundred records were diagnosed as large bowel obstructions (16.5%) and 80% were male (volvulus: 84%, cancer: 60%). Their age range was 16-105 years, (mean=48 years). Volvulus occurred in 152 (76%) patients (sigmoid, 87%; cecum, 9%; transverse colon, 2.5% and splenic flexure, 1.3%). Colon cancer was diagnosed in 30 patients (15%); and the other causes were adhesion, 3.5%; hernia, 1.5%; fecal impaction, 2%; TB, 1% and ileosigmoid knot, 1%) compromising the remained 9% of cases. Conclusion: Sigmoid volvulus was the most common cause of colonic obstruction in south of Iran and male predominance was seen in both volvulus and cancer groups.