: Interstitial pregnancy is a rare condition of tubal pregnancy with a mortality rate of 2-2.5%  that can easily be misdiagnosed. The prevalence of interstitial pregnancy is 0.8% in normal population and it increased during the past few decades due to reproduction techniques development even up to 11% in groups of women after in vitro fertilization. A comprehensive MEDLINE and OLDMEDLINE search covering years 1950-2005 using query terms "interstitial", "pregnancy" and "adnexectomy" identified only 10 cases reported in worldwide literature. The first treatment of interstitial pregnancy used to be a resection of the uterus body via laparotomy. Along with the evolution of sensitive biochemical assays, imaging technologies and the development of operative techniques, the management of interstitial pregnancy became less invasive. We report a case of spontaneous left interstitial pregnancy after left adnexectomy due to left ovarian tumor of borderline malignancy.