Cervical incompetence is defined as an abnormal dilatation of the cervical canal at the body-neck junction with no pain or blood loss and in the absence of uterine contractile activity. Cervical incompetence is the frequent cause of abortion in the second trimester and premature delivery, with adverse fetal prognosis. Usually, three causative factors are considered: traumatic, constitutional, dysfunctional. While in multiparous women the medical and remote obstetric history poses the diagnostic suspicion, in primigravidae, in the absence of previous risk factors (traumas, malformations, etc) early diagnosis may allow prompt treatment with a better prognosis. Hysterosalpingographic (tunnel-shaped cervix or appearing as an inverted sac, diameter of internal uterine orifice) but especially sonographic findings (cervical length, dilated endocervical canal, tunnel-shaped internal uterine orifice, herniation of the amniotic sac into the endocervical canal) represent the most significant radiologic signs. The radiologist should be able to recognize the typical imaging of this condition to select the patients who should undergo serial controls in time since the start of the second trimester of pregnancy, or to indicate a suitable treatment based on sonographic signs suggestive for incompetence identified before the clinical exam. This is the present correct approach while waiting for future clinical and technological developments of three-dimensional sonography and MRI which will be able to detect those changes in cervical connective structures responsible for incompetence and still not identified by any imaging procedure.