Pregnancy in the interstitial part of the tube, i.e. in the part of the tube that lies in the uterine wall, is relatively rare. Thus, according to Rosenthal's compilation statistics, among 1,324 cases of ectopic pregnancy, 3% were interstitial. Lawson-Tait notes only one case of interstitial pregnancy per 100 cases of ectopic pregnancy. In Povival Institute (Prof. Ott) from 1904 to 1907 on 71 cases of ectopic pregnancy also met only one case of interstitial pregnancy. Gubarev saw the latter only once in his practice. Werth did not see it even once. During the 35 years of the existence of the Obstetrical Clinic of the Leningrad State Clinical Institute, the first case of interstitial pregnancy was described only in 1924. The four cases of interstitial pregnancy described below are also the first in the last 28 years of the Kazan Obstetrical Gynecological Clinic.