Infected urachal cyst is a rare disorder. While the urachal cyst is usually aymptomatic, the infected cyst may mimic a variety of acute intraabdominal infection. We have experienced a case of infected urachal cyst in a 59 year old woman complaining of localized abdominal pain and discharge through the abdominocutaneous fistula under the umbilicus. Abdominal sonogram and abdominal computerized tomography demonstrated a cystic mass posterior to central abdominal wall. Pus was drained from the cystic lesion through the track to fistula site on the skin.