Acute appendicitis remains one of the most difficult diagnoses to make in the Emergency Department. We present a puzzling and unusual case. A 47-year-old man had several hours of acute abdominal pain in the right upper quadrant, point tenderness in the right midquadrant on examination, and normal chemistries. Early appendicitis was suspected and a computed tomography (CT) scan of the abdomen was obtained. Appendicitis was not seen. What was evident was a retroperitoneal lipoma estimated to weigh 10 pounds. The general surgeon was consulted who believed that operation was necessary in light of the patient's continuing abdominal pain and the presence of the mass. Masses this large could cause pain from local compression of structures, or ischemia of the mass from outgrowing its blood supply. In surgery, a lipoma was observed that filled most of the retroperitoneum and displaced all the contents of the abdomen, including the cecum and its appendix. Also present was an acute appendicitis. On retrospective analysis of the CT scan, the appendicitis was evident but atypically located in the epigastrium. This case illustrates once again that the CT scan is a useful diagnostic adjunct for the diagnosis of new onset abdominal pain and specifically for appendicitis.