A method is described for determination of the stress-relaxation characteristics of the cervix uteri of nongravid women after almost stepwise dilatation of the cervical canal by a water-filled balloon. The stress relaxation is followed by measurement of the pressure decay in the same balloon. Application of this atraumatic technique to women with a normal cervix and women known to have an incompetent cervix yields diagnostic ranges of various parameters, in particular a time constant and the elastic ratio. The technique seems promising for easy detection of cervical incompetence, allowing suitable measures to be taken for prevention of immature deliveries. A mechanical model of the tissue of the ostium internum has further been developed on the basis of the measured characteristics.