Interstitial pregnancy is ectopic pregnancy which occurs within the intramural (interstitial) part of the uterine tube. The frequency of its occurrence is 3-4% of all ectopic pregnancies. It is also significant because of a long asymptomatic period and common ending with the rupture of the uterine horn as a serious complication. Mortality after this type of ectopic pregnancy is about 2,5%. This paper presents a case of a 29- year-old patient hospitalized for suspected ectopic interstitial pregnancy in the left uterine horn. Her anamnesis showed the left tube pregnancy ended with salpingectomy after the rupture of the uterine tube. The patient was examined both clinically and by ultrasound, her ß-HCG level was being monitored, and after an adequate preoperative preparation, she underwent a surgery. Surgical intervention consisted of the incision of pregnancy-altered uterine horn, curettage and evacuation of ovulary tissue, which saved the uterine horn. Timely diagnosis of interstitial pregnancy can prevent its possible serious complications.