An instrument for the continuous measurement of cervical dilatation is described. The principle of operation, being that of mutual inductance, utilises two coils, one on the posterior lip of the cervix and the other on the anterior, the axes of these coils being kept parallel by a flexible linkage. A magnetic field, from the primary coil being driven with a lOkHz alternating current of constant amplitude, induces a voltage in the secondary coil. This voltage whose magnitude decreases as the distance between the coils increases, is used by the instrument for the determination of cervical dilatation. A cervical dilatation recording from a multiparous patient is presented and discussed.