Heterotopic pregnancy is defined as intrauterine pregnancy that coexists with an ectopic pregnancy. It is relatively rare condition in spontaneous pregnancy. But its natural incidence is increasing with development of assisted reproductive technology (ART). The early diagnosis of heterotopic pregnancy is very difficult. There is high maternal morbidity and mortality resulted from intra-abdominal bleeding after rupture of ectopic pregnancy. So we should consider both heterotopic pregnancy and normal intrauterine pregnancy regardless of history of ART procedure. We experienced two cases of heterotopic pregnancy in patients with acute abdominal pain who became pregnant naturally without ART. First patient was 45-year old with hypovolemic shock, and the second was 33-year old from postabortal state, so we report these cases with a brief review of literatures. Early diagnosis and intervention in heterotopic pregnancy can prevent from endangering the life of woman as well as the ongoing pregnancy.