The endometrial stripe, also known as the endometrial lining or endometrium, is a part of the uterus that can be seen on imaging tests such as ultrasounds and MRIs. It is a complex structure of the womb with its own microenvironment that allows it to perform its unique function of supporting a fertilized egg. The appearance and thickness of the endometrial stripe depend on the menstrual cycle and age of the woman. During the menstrual or early proliferative phase, the endometrial stripe is thin and looks like a straight line. In the late proliferative phase, it develops a trilaminar appearance. For women of reproductive age, the endometrial stripe can be anywhere from slightly less than 1 millimeter to slightly more than 16 millimeters in size, depending on the phase of menstruation. In post-menopausal women, the endometrial stripe is supposed to be 8 to 11 millimeters thick, and a stripe more than 11 millimeters is considered thick. Abnormally thick stripes could be a sign of cancer. Endometrial stripe ≥15 mm may be a useful preoperative marker to identify patients at higher risk for concurrent endometrial cancer. If a woman experiences abnormal bleeding, such as regular heavy menstruation, irregular menstruation, prolonged menstrual bleed, bleeding in the middle of the cycle, bleeding after sexual intercourse, markedly reduced or even total absence of menstruation, she should seek help from a gynecologist.