A case of adenocarcinoma of the splenic flexure during pregnancy is reported. A 27-year-old woman was admitted at 34 weeks of pregnancy with abdominal pain and vomiting. 36 hours after normal delivery an emergency exploratory laparotomy was performed for intestinal obstruction. A huge tumor of the splenic flexure with retroperitoneal extension was found. She died 1 year later of metastatic disease. Delay in diagnosis and complications of colonic cancer are more prevalent in pregnancy. While colonic carcinoma during pregnancy is extremely rare, it should be included in the differential diagnosis of colonic symptoms. The 24th case of this type is reported.