Hydatid disease is an endemic disease in certain areas of the world. It is located mostly in the liver. Spontaneous rupture of the hydatid cyst into the peritoneum is a rare condition, which is accompanied by serious morbidity and mortality generally. We present herein a case with a spontaneous rupture of a hepatic hidatid disease into the peritoneum without any serious symptoms. A 15-year-old boy was admitted to the emergency room with a mild abdominal pain lasting for a day. Physical examination revealed only mild abdominal tenderness. There was no history of trauma or complaints related to hydatid diseases. Ultrasonography showed a large amount of free fluid and a cystic lesion with irregular borders in the liver. He was operated on. Postoperative albendazol therapy was given for 2 mo. No recurrence or secondary hydatidosis was seen on CT investigation in the 3rd, 6th and 12th mo following surgery. Hydatid disease is an endemic disease in certain areas of the world. It is located mostly in the liver. Spontaneous rupture of the hydatid cyst into the peritoneum is a rare condition, which is accompanied by serious morbidity and mortality generally. We present herein a case with a spontaneous rupture of a hepatic hidatid disease into the peritoneum without any serious symptoms. A 15-year-old boy was admitted to the emergency room with a mild abdominal pain lasting for a day. Physical examination revealed only mild abdominal tenderness. There was no history of trauma or complaints related to hydatid diseases. Ultrasonography showed a large amount of free fluid and a cystic lesion with irregular borders in the liver. He was operated on. Postoperative albendazol therapy was given for 2 mo. No recurrence or secondary hydatidosis was seen on CT investigation in the 3rd, 6th and 12th mo next surgery.